* Viper does large amounts of magic damage over time, meaning that if a Necrophos uses Ghost Shroud, Viper's abilities will greatly reduce Necrophos survivability, and may actually kill him.
* By the same token, Viper can use his Viper Strike on Necrophos if he attempts to heal himself with Ghost Shroud, and depending on any other effects Necrophos may have from him, (IE:Poison Attack,Corrosive Skin), Viper can often kill Necrophos while he is in his Ghost Shroud.
* Viper's Corrosive Skin helps him take reduced damage from all of Nercophos spells that deal magical damage, which is Necrophos's only source of damage.
Additional:
* Nethertoxin prevents Heartstopper Aura from dealing damage or healing Necrophos.
* Viper's magic damage is amplified whenever Ghost Shroud is used.
* Corrosive Skin makes Viper tankier against Death Pulse and Reaper's Scythe.

* Diffusal Blade is a core item on Phantom Lancer. And when combined with his numerous illusions, it allows him to rapidly deplete Necrophos's mana, rendering Necrophos incapable of doing anything.
* It can be difficult to single out the true Phantom Lancer among his army, giving Necrophos a hard time with aiming his ultimate.
* Even if his illusions are defeated, Phantom Lancer can simply create more of them at his disposal with almost no issues.

* Doppelganger can be used to easily dodge Light Strike Array if timed correctly.
* Phantom Lancer can quickly deplete Lina's mana pool with his illusions and deal massive damage from it simultaneously since Phantom Lancer is a natural Diffusal Blade carrier.

* Nethertoxin prevents buildup of Fiery Soul stacks.
* Corrosive Skin provides magic resistance against Lina's spells.
* Poison Attack and Viper Strike can burn away Lina's small health pool.

* Phantom Lancer's illusions destroy Refraction charges very quickly.

* The damage over time from Viper's Poison Attack and Viper Strike rapidly wear down Refraction charges, allowing Templar Assassin to be damaged. Additionally, Corrosive Skin causes her attacks to apply damage overtime on her as well.
* Nethertoxin is a big threat to Templar Assassin. Her initially low range making it very hard to deal against Nethertoxin in the laning phase. At any stage of the game, a Nethertoxin can always force her to undo her Meld.
Additional:
* All of Viper's abilities quickly burn through Refraction charges.
* Templar Assassin's short range, aside from Psi Blades' spill damage, makes her vulnerable to Poison Attack harassment.
* Templar Assassin traditionally forgoes health and armor items for damage. Outside of Black King Bar, Viper will almost always be able to kill her when Refraction is down.

* Nethertoxin breaks Multicast.
* Corrosive Skin minimizes the damage from Ignite and Fireblast.

* Ogre Magi has no undispellable AoE damage or disables and has nothing to deal with Phantom Lancer's illusions.
* Doppelganger disjoints and dispels Ignite.

* Phantom Lancer has higher mobility and the ability to reset any fights with Doppelganger can be a nuisance for spectre to fight against.
* Phantom Lancer is a natural carrier of Diffusal Blade and Manta Style, which is outright nullify Desolate. In fact, Phantom Lancer will always have illusions with him at anytime, thus further exacerbated the problem.
* Although Spectre is largely AoE oriented, unfortunately, they are damage-over-time (DoT) rather than burst AoE damage. Without any effective ways to quickly destroy illusion and reveal the real hero, Spectre has little availability to manfight Phantom Lancer at any points in the game.
* Spectre often relies on Spectral Dagger as a pseudo-mobility skill. With her low mana pool and complete dependence on it to catch enemy team, she will soon find herself unable to do anything significant once her mana pool is completely drained.
* Doppelganger can be used to dispel the slow from Spectral Dagger, thus completely render it useless.

* Nethertoxin disables Desolate and Dispersion, leaving Spectre with far less damage output and damage mitigation in engagements.
* Spectre is one of the weakest heroes at early levels. Viper can stifle her farm with early fights before Spectre purchases any major items.
Additional:
* Nethertoxin disable passives, negating Spectre's damage and survivability by removing both Dispersion and Desolate.
* Due to Haunt and Radiance's burn, Spectre is heavily susceptible to being persistently slowed and damaged by Corrosive Skin without even directly attacking Viper.
* Poison Attack and Viper Strike further slow Spectre's movement speed to a crawl, while his improved magic resistance means he can easily shrug off Radiance's burn.

* Nethertoxin breaks Sniper's passives.
* Viper Strike together with Poison Attack can slow Sniper and tears through his low health and mobility.

* Phantom Rush grants Phantom Lancer the mobility to close in the distance between Sniper.
* Phantom Lancer can dispel and disjoint Sniper's Assassinate easily with Doppelganger and causes confusion to Sniper with the latter effect of creating an additional of 2 illusions.
* Phantom Lancer's Juxtapose easily can overwhelm Sniper, as his damage is mostly single-targeted.

* Corrosive Skin minimizes the damage Viper takes from all of Disruptor's skills.

* Doppelganger lets Phantom Lancer instantly escape from Kinetic Field.
* Doppelganger is one of the most reliable ways to dodge Glimpse, other than spell immunity.
* Doppelganger dispels Thunder Strike.
* However, even with the negation of the rest of his kit, Static Storm (especially when upgraded with Aghanim's Scepter) remains as one of the strongest lockdowns against Phantom Lancer, and as such Disruptor must never be underestimated.
Additional:
* Doppelganger is a very reliable tool against Glimpse, enabling him to dodge it consistently.
* Doppelganger also allows Phantom Lancer to escape from Kinetic Field so long as there isn't a Static Storm on top of him.

* Viper's poison abilities can slow Bounty Hunter's movement speed and allows to chase him with True Sight items.
* Nethertoxin can break Jinada, and the silence from level 25 prevents Bounty Hunter from using all of his spells.

* Doppelganger dispels Track.
* Bounty Hunter also has no area of effect abilities to help with the illusions.

* Nethertoxin disables Vengeance Aura.
* Vengeful Spirit has no mobility spells aside from Nether Swap, which Viper can take advantage of with his slows.
* Viper can easily bully Vengeful Spirit out of a lane with Poison Attack.
Additional:
* Nethertoxin prevents the attack damage bonus from Vengeance Aura and the components of Nether Swap.
* Both Magic Missile and Wave of Terror are counteracted by Corrosive Skin, making Vengeful Spirit's fighting harder against Viper.

* Vengeful Spirit has no strong AoE nuke or disable against Phantom Lancer's Illusions.
* Phantom Lancer is a natural Diffusal Blade carrier, which reduces Vengeful Spirit's low mana pool very quickly, leaving her defenseless.
* Doppelganger can dodge Vengeful Spirit's abilites.
* Phantom Rush with his illusions can chase Vengeful Spirit efficiently.

* Nethertoxin negates Essence Shift and the regeneration aspect of Shadow Dance.
* Dark Pact doesn't mean a lot against Viper's ubiquitous slows.
* Viper becomes a relevant presence in team fights before Slark can procure his standard items (e.g. Shadow Blade).

* Slark has no sustained AoE to fight off Phantom Lancer's illusions as they continually spawn.
* Spirit Lance can give vision of Slark by spawning an illusion, making it harder for him to juke and gain the passive bonus from Shadow Dance.
* Phantom Rush helps Phantom Lancer chase down Slark if he tries to escape with Pounce.
Additional:
* Slark has no sustained AoE damage to deal with a lot of Phantom Lancer's illusions.
* Doppelganger lets Phantom Lancer dodge Dark Pact and Pounce and partially wastes the duration of Shadow Dance.
* Spirit Lance can give vision of Slark via spawning an illusion, making it harder for him to juke and gain the passive bonus from Shadow Dance.
* Phantom Rush helps Phantom Lancer chase down Slark when he jumps away with Pounce.

* Ursa has no sustained AoE to deal with illusions, it becomes worse since Phantom Lancer can create more illusions in a matter of seconds.
* Diffusal Blade can be used to drain Ursa mana. This is a standard item for Phantom Lancer in every match.
* Doppelganger applies basic dispel on Phantom Lancer, which will remove the slow from Earthshock. It also resets fights with more illusions, making hard for Ursa to hit the real Phantom Lancer.
* Manta Style create two more illusions and also applies basic dispel, further complicate the problem for Ursa to deal with.

* Nethertoxin breaks Fury Swipes, making Viper a decent counter to Ursa in a laning stage.
* Viper Strike is a strong, undispellable slow, making it much easier to kite Ursa for everyone.

* Phantom Lancer's illusions will quickly destroy multiple layers of Gravekeeper's Cloak.
* Visage has no mobility mechanisms, making him a prime target for Phantom Rush.

* Nethertoxin cuts off Gravekeeper's Cloak, Visage's primary defense mechanism.
* Viper can ignore Grave Chill's attack speed slow with his magic damage output.
Additional:
* Since Visage is a slow hero, Viper can easily kite him with Poison Attack and Viper Strike while successfully chipping away at Gravekeeper's Cloak.
* Nethertoxin removes all layers of Gravekeeper's Cloak, leaving Visage exposed.
* Corrosive Skin makes Viper highly resistant to Soul Assumption.

* Illusions can be sent out to destroy Techies mines.

* Corrosive Skin will protect Viper from Techies' magical damage.
* Even though Reactive Tazer will disarm Viper if he attacks Techies with Poison Attack, he does lots of damage with his other abilities that can still kill Techies.

* Doppelganger can dispel Leech Seed. It can also destroy large amounts of trees, counteracting Nature's Guise and Eyes in the Forest.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Heroes with illusions can overwhelm Huskar: Phantom Lancer, Anti-Mage, Arc Warden, Chaos Knight.

* Nethertoxin disables Berserker's Blood, which Huskar relies upon for attack speed and healing.
* The damage from Burning Spear and Life Break is largely absorbed by Corrosive Skin. It also will return some damage, making it risky to use Burning Spears in the laning stage.
* Because Huskar wants to be on low health for Berserker's Blood, he is particularly vulnerable to Poison Attack.
Additional:
* His Poison Attack is very useful against Huskar, since he tends to stay at low health.
* Nethertoxin disables passive skills like Berserker's Blood.
* It is dangerous for Huskar to jump on Viper because Corrosive Skin and Viper Strike with the slowdown of movement and attack speed which usually will be deadly for Huskar.

* Heroes with damage-increasing passive abilities, such as Viper and Riki, will usually kill Silencer in a short time before he even has time to set up his abilities.

* Due to Phantom Rush and Juxtapose being passives and not affected by silence, a Phantom Lancer with a Diffusal Blade can easily kill Silencer.

* Phantom Lancer's illusions can make it difficult to Doom the original. Should Doom figure out the original hero, the illusions can make it difficult to cast any abilities, as their hitboxes can be used to body-block the Phantom Lancer.
* Phantom Lancer is an ideal Diffusal Blade carrier. With it, he can quite easily deplete Doom's already poor mana pool, potentially making him unable to cast his abilities to escape, retaliate or heal.
* Doom lacks any effective ability to clear waves of creeps and illusions, as the vast majority of his abilities are single-target. Without an answer, Doom may find it difficult to deal with Phantom Lancer's presence.

* The slow applied from Corrosive Skin offsets the movement speed bonus granted by Scorched Earth and the tick-based damage from Infernal Blade and Doom will continually slow Doom down. This allows Viper, much like Sniper, to 'kite' Doom and keep him at a safe distance between the two. Additionally, Corrosive Skin applies an attack-speed slow which is fairly crippling to a hero such as Doom that, naturally, has a high base attack-time, poor agility gain and builds little attack-speed items.
* Since Doom does not disable auto-cast abilities, Viper's Poison Attack will continue to work. Doom may find it hard to close the distance between himself and Viper, and thusly difficult to effectively lockdown and continually deal damage through his abilities.

* Corrosive Skin minimizes the damage Viper takes from all of Ancient Apparition's abilities.
* Ancient Apparition's slow movement speed, squishy nature, and lack of escape abilities can easily be taken advantage of through Poison Attack and Viper Strike.

* Phantom Lancer can dispel or escape from Cold Feet with Doppelganger and Phantom Rush, respectively. Phantom Lancer also frequently builds a Manta Style which dispels Cold Feet.
* Ancient Apparition has trouble dealing with Phantom Lancer's illusions due to a lack of Area of Effect damage other than Ice Blast.
* Phantom Lancer tends to build a Diffusal Blade, which greatly amplifies his damage against Ancient Apparition due to Ancient Apparition's high mana pool.
* Ancient Apparition has no escape/mobility mechanisms, making him an easy target for Phantom Lancer at any stage of the game.

* Hand of God has a long cooldown, so damage over time spells can be hazardous for Chen, forcing him to use it prematurely: Jakiro, Venomancer, Viper, Dazzle, Phoenix.

* Illusion and heroes with summons are difficult to kill with Chen's single-target offensive spells: Terrorblade, Phantom Lancer, Chaos Knight, Broodmother, Naga Siren, Lycan, Visage. However, Chen can convert enemy summons with Holy Persuasion, as long as they don't bunch up.

* Nethertoxin prevents the buildup of Jingu Mastery stacks.
* Monkey King's high base movement speed is of little worth against the array of slows Viper possesses.
* All of Viper's magical damage over time stops Monkey King from using Tree Dance. It also ignores the extra armor bestowed by Wukong's Command.
Additional:
* Nethertoxin prevents the buildup of Jingu Mastery stacks.
* Viper's poison magical damage-over-time stops Monkey King from using Tree Dance. It also ignores the extra armor bestowed by Wukong's Command.

* Heroes that can destroy trees will deny Monkey King spots to jump on, or cause him to fall: Windranger, Nature's Prophet, Phantom Lancer

* Doppelganger dispels Sticky Napalm and Flamebreak.
* There are usually way too many illusions for Batrider to lasso the real Phantom Lancer, since the illusions' hitboxes also body block the real Phantom Lancer.

* Phantom Lancer with Diffusal Blade will very quickly burn Medusa's mana, making Mana Shield significantly less effective.
* Doppelganger's 1 second invulnerability can be used to dodge Medusa's petrification from Stone Gaze, as well as Mystic Snake.
* Phantom Lancer's illusions outnumber Medusa's targets from Split Shot, likely shielding your team in the process.

* Nethertoxin breaks both Necromastery and Presence of the Dark Lord, reducing his damage massively.
* Corrosive Skin gives Viper bonus Magic Resistance against Shadowraze and Requiem of Souls.
* Viper can easily take advantage of Shadow Fiend's lack of escape and mobility spells with Viper Strike and Poison Attack. Poison Attack also serves as a great way to harass Shadow Fiend.

* Tiny has low movement speed and attack speed, making him vulnerable to Viper's slows.
* Corrosive Skin provides magic resistance to lower Tiny's magic burst damage.

* Doppelganger. lets Phantom Lancer jump in and out of Power Cogs.
* Clockwerk's low mobility makes him an easy target for Phantom Lancer to rush on, and overwhelm with clones.
Additional:
* Battery Assault's damage is dispersed against Phantom Lancer's illusions.
* Phantom Lancer can blink out of Power Cogs with Doppelganger.
* When chasing, a Phantom Lancer can close in with Phantom Rush and burn down Clockwerk's mana with Diffusal Blade, rendering him helpless before he has a chance to erect a defensive Power Cogs.
* Because Clockwerk does not like to buy items to deal with multiple enemies at once, like Battle Fury, Maelstrom and Mjollnir, he will be unable to deal with Phantom Lancer's illusions coming from Juxtapose.

* Although Outworld Destroyer will typically destroy Phantom Lancer's illusions in one shot, Phantom Lancer spawns too many of them for Outworld Destroyer to deal with. However, be careful about initating on Outworld, as Sanity's Eclipse will erase your illusions and deal massive damage to you. He can then follow up with Astral Imprisonment and Meteor Hammer.
Additional:
* Doppelganger and Juxtapose allows Phantom Lancer to initiate on Outworld Destroyer, and, although Arcane Orb will normally destroy his illusions instantly, Phantom Lancer will spawn too many to deal with, without using Sanity's Eclipse
* Outworld Destroyer has very little AOE ability, His Astral Imprisonment with Aghanim's Scepter is his primary AOE, and it does too little damage to eliminate Phantom Lancers illusions

* Corrosive Skin means Viper can often outlast Venomancer in a battle of attrition.
* Venomancer has no mobility without items, which makes him vulnerable to constant slows.

* Juxtapose and Doppelganger conjures too many illusions for Dazzle to deal with, given he has no inherent movement- or AoE-abilities.
* Phantom Rush and Spirit Lance allow Phantom Lancer to trivially catch Dazzle even in the back line of a fight.
* Phantom Lancer has high base armor which counters Dazzle's physcial damage based spells in lane.

* Void's slow is dispelled by Doppelganger or counteracted by Phantom Rush.
* Spirit Lance's and Diffusal Blade's slow reduces Night Stalker's mobility and helps him or his ally escape if they're inflicted by Void or Crippling Fear.
* Night Stalker has no AoE abilites to take out Phantom Lancer's illusions. Even if Night Stalker gets an Aghanim's Scepter, there will be way too many illusions for Night Stalker to handle.

* Because Poison Attack has no cooldown, Aphotic Shield is ineffective as a hard dispel.
* Nethertoxin prevents Borrowed Time from activating passively and blocks Curse of Avernus

* Phantom Lancer's Doppelganger has a low cooldown and applies a basic dispel on PL, making it hard to keep Corrosive Haze on him.
* Phantom Lancer usually purchases Manta Style which provides another basic dispel to remove Corrosive Haze with.
* Besides Slithereen Crush, Slardar does not have another way to deal with illusions and has a low mana pool, which allows Phantom Lancer with Diffusal Blade to quickly build up illusions while draining Slardar's mana.
* Phantom Rush outruns Guardian Sprint, forcing Slardar to Blink away or use Slithereen Crush defensively to avoid being killed.

* Corrosive Skin minimizes the damage from Impale and Mana Burn.
* Nyx Assassin cannot survive several poison damage-over-time, even Spiked Carapace is activated.

* Phantom Lancer's many illusions will easily destroy Tombstone, provided he has sufficient farm.
* He also has no ways of dealing with the illusions, since Decay doesn't steal strength from illusions.

* Lone Druid and his Spirit Bear lack mobility, and are easy overwhelmed after being slowed by Diffusal Blade.
* Savage Roar is useless since Phantom Lancer can return to fight him again with his Phantom Rush.

* Phantom Rush lets Phantom Lancer get close quickly and disable Marksmanship.
* One of Phantom Lancer's core items (Manta Style) can dispel Gust.

* Viper's Nethertoxin disables Cloak and Dagger, negating Riki's invisibility and much of his damage. It also makes him more vulnerable to magic damage, which does not go well with Riki's low health pool. With the talent applied, he can't even blink to safety or hide with Tricks of the Trade.
* Corrosive Skin makes it hard for Riki to chase Viper and attack him due to the attack speed slow.
* Viper Strike stays on Riki even after he goes invisible.
* Poison Attack makes it risky for Riki to get last hits and can make the laning phase difficult for him.

* Heroes with break can disable Untouchable for a while: Doom and Shadow Demon (via Aghanim's Scepter), Viper, Shadow Shaman with Hex Breaks talent.

* Heroes with no AoE abilities will struggle against Phantom Lancer: Phantom Assassin, Broodmother

* Heroes that can apply early pressure before Phantom Assassin has farm are massive threats: Axe, Viper, Meepo, Pugna, Slark etc.

* Diffusal Blade lets Phantom Lancer drain Wraith King's mana, preventing Reincarnation from triggering until he buys an Aghanim's Shard.
* Wraith King is bad against illusions-based heroes, as Wraithfire Blast is his only single-target disable and can get overwhelmed easily.
* Doppelganger can disjoint Wraithfire Blast.
Additional:
* Doppelganger disjoints Wraithfire Blast.
* Wraith King is not good at handling illusion-based heroes, as his only disable is single-target.
* Phantom Lancer tends to get Diffusal Blade, leaving Wraith King no mana to reincarnate.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Heroes with Attack speed decreasing skills: Jakiro, Viper Lich

* Chaos Knight's single target abilities are difficult to target against Phantom Lancer's illusions.
* Chaos Knight's lack of mobility makes him an easy target for Phantom Lancer to Phantom Rush and drain his already low mana pool.
Additional:
* Juxtapose allows Phantom Lancer to overwhelm Chaos Knight due to his single-target abilities.
* Doppelganger can be used to dodge Chaos Bolt.
* Since Phantom Lancer builds Diffusal Blade often, it can quickly drain Chaos Knight's low mana pool, leaving him unable to cast spells.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer

* Any heroes that naturally buy Diffusal Blade like Phantom Lancer or have a mana break talent is a big issue for Pudge because of his low mana pool.

* Illusion-based heroes are effective against Omnislash and Juggernaut's single-targeted damage: Naga Siren, Chaos Knight, Terrorblade,Phantom Lancer.

* Skywrath mage also has a terrible time fighting against anything that isn't a hero. As Mystic Flare only affects heroes, his skills are mostly target-based and he has terrible strength and agility, he can easily be kited or harassed by illusion-based heroes like Chaos Knight and Phantom Lancer, or by Heroes that summon other units like Lone Druid, Lycan and Beastmaster.

* Heroes who are not easily crippled by Fate's Edict or Fortune's End, such as Timbersaw, or those who can dispel them, such as Phantom Lancer, can kill Oracle unhindered.

* Heroes with summons or illusions makes Sacred Arrow harder to land: Shadow Demon, Phantom Lancer, Nature's Prophet.

* Illusion heroes, such as Naga Siren, Phantom Lancer, Chaos Knight, Terrorblade will become strong against Tinker in the late game when Tinker's only area of effect damage, March of the Machines, ceases to kill illusions quickly. Without Aghanim's Scepter Tinker is forced to defensively disarm heroes with Laser, leaving illusions free to deal physical damage which Tinker's low armor makes highly effective. In addition, Mjollnir or Battle Fury, two common pickups against illusion heroes, don't work well on Tinker at all.

* Heroes who can harass Omniknight out of lane will keep him weak in the mid game: Viper, Venomancer, Clinkz

* Nethertoxin disables Bulwark entirely, making Mars far less tanky. Using Nethertoxin inside Arena of Blood may discourage enemies from following up with Mars' initiation.
* Rod of Atos is currently common on Viper and keeps Mars in position long enough to be killed.
* Beware that Viper is not very tanky earlier in the game, so positioning against Mars is important since a well-timed Spear of Mars can be the end of Viper.
Additional:
* Nethertoxin breaks the damage block from Bulwark.
* Poison Attack and Viper Strike's slows make it difficult for Mars to contribute to fights due to his low mobility.

* Doppelganger allows Phantom Lancer to dodge an incoming snowball.
* Phantom Lancer usually buys a Diffusal Blade, which is very effective against Tusk's low mana pool.
* Phantom Lancer usually buys Manta Style which can also dodge an incoming snowball, much like Doppelganger.

* Corrosive Skin counters Zeus in lane by canceling the effects of Clarity as Zeus relies on Arc Lightning to farm and secure last hits.
* Corrosive Skin also increases Viper's magic resistance to shrug off Zeus's magical nukes.
* Nethertoxin breaks Static Field.
* Due to Zeus' poor mobility, Viper Strike will cripple Zeus and will allow Viper and his teammates to land a lot of attacks.
Additional:
* Corrosive Skin severely reduces Zeus's damage output throughout the game.
* During the laning stage, Viper can abuse Zeus' reliance on spells by hugging the creep wave. Zeus will take constant damage over time from Corrosive Skin unless he drives Viper from the lane or returns to farming in his absence.
* Prior to buying Blink Dagger or Force Staff, Zeus is fragile and possesses low mobility. Any of Viper's numerous slows can set up an easy kill.

* Nethertoxin disables Dawnbreaker's Luminosity|Dawnbreaker. Since she's a melee hero, she needs to close gap to attack and Nethertoxin will be bad for her since she cannot heal.
* Viper Strike and Poison Attack will severely slow her down and combined with Nethertoxin, it will be her death sentence (unless her Celestial Hammer or Solar Guardian are off cooldown). Besides that, chasing her down will be easy due to the slow.

* Viper's skill set makes him an effective early game ganker against Anti-Mage before he is sufficiently farmed.
* Viper's Corrosive Skin and low mana pool causes him to take little damage from Mana Void.
* Nethertoxin disables Mana Break and Counterspell, weakening both his offense and defense.

* One of Arc Warden's hardest counters, Arc Warden, who has primarily single target damage, will struggle tremendously against Phantom Lancer:
* Flux is paused if even one illusion remains near Phantom Lancer. It can also be dispelled with Doppelganger.
* Phantom Lancer can also easily dodge an activated Spark Wraith, or use his illusions to trigger it safely.
* Phantom Rush allows Lancer to quickly close gap to get inside of Arc Warden's Magnetic Field.
* Phantom Lancer and his clones are able to quickly drain Arc Warden of his mana with a Diffusal Blade. This means Warden's Tempest Double will also be summoned without mana.
Additional:
* Doppelganger dispels Flux.
* Phantom Rush closes the distance between Phantom Lancer and Arc Warden.
* Juxtapose overwhelms Arc Warden and nullifies his kit which is only effective against isolated enemies.

* Nethertoxin disables Bristleback and prevents Warpath from building stacks. Besides losing his defensive passive, Bristleback also loses his ability to build up damage over lengthy battles.
* Viper can perpetually kite Bristleback with Poison Attack and Viper Strike.
Additional:
* Nethertoxin disables Bristleback's passive.
* Viper Strike and Poison Attack slow down Bristleback's movement speed so he's unable to get out from Nethertoxin.

* Nethertoxin prevents Timbersaw from gaining stacks on Reactive Armor.

* Dragon Knight is easily harassed by Poison Attack after the laning stage ends.
* Corrosive Skin protects Viper from Breathe Fire and returns damage.
* Nethertoxin mitigates Dragon Blood, Dragon's Knight main source of armor and health regeneration.
* Between Poison Attack and Viper Strike, Viper can keep Dragon Knight permanently slowed even in Elder Dragon Form.
Additional:
* In the early game, a Dragon Knight without Black King Bar is basically defenseless against Viper.
* Viper can harass Dragon Knight at any time with his Poison Attack.
* Corrosive Skin reduces damage from Dragon Fire and inflicts damage to him.
* Nethertoxin disables Dragon Blood, negating his main survivability.
* Viper Strike and Poison Attack can severely slow him down even with his Elder Dragon Form.

* Phantom Lancer creates way too many illusions for Pugna's Life Drain to destroy, overwhelming him easily.
* Doppelganger can dodge Nether Blast or dispel Decrepify.
* Diffusal Blade is a common item for Phantom Lancer to burn Pugna's large mana pool and deals a large amount of damage in the process.
Additional:
* Though Life Drain instantly destroys illusions, Phantom Lancer creates way too many for Pugna to handle.
* A good Phantom Lancer will also dodge your Nether Blast with Doppelganger.
* Phantom Lancer is the most natural Diffusal Blade carrier to burn Pugna's very large pool of mana away and deal a large amount of damage in the process.

* Heroes with dispels: Legion Commander, Oracle, Slark, Phantom Lancer

* Viper's Poison Attack and Viper Strike that can slow Razor, and is one of the few heroes that can keep him immobile.
* Altogether, Viper's skills reduce Razor's attack speed, heavily reducing the benefit of the damage drain from Static Link.
Additional:
* Storm Surge is counteracted by Nethertoxin, leaving Razor without faster MS.
* Static Link's damage drain doesn't bother Viper a lot as most of his early to mid game damage is magical.

* Although Phantom Lancer will generate strong illusions, and you can also break his Juxtapose with an Aghanim's Demonic Purge, you have a small chance of guessing which is the real Phantom Lancer after he uses Doppelganger.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Phantom Lancer can effortlessly overwhelm Morphling with a large number of illusions. It becomes even more effective with {Item ID:Diffusal Blade}, which takes away his mana in the process.
* Doppelganger can be used to dodge Adaptive Strike combo and create confusion with two additional illusions.
* Eye of Skadi can be bought to slow and negate the health regeneration from Attribute Shift, and a common item for Phantom Lancer.

* Poison Attack makes it hard for Void Spirit to lane against him.
* Corrosive Skin reduces the magical damage from Void Spirit's spells.

* Poison Attack and Viper Strike slows Axe significantly, and puts his Blink Dagger on cooldown, preventing him from initiating.
* Nethertoxin can break Counter Helix.
Additional:
* Nethertoxin prevents Counter Helix from triggering, which significantly lowers Axe's damage output in the early to mid game.
* Viper's various slows and damage over time prevents Axe from initiating as well as putting his Blink Dagger on cooldown.

* Corrosive Skin makes Viper receive less damage from Invoker's spells
* Viper can harass Invoker with his Poison Attack in the early game.
* Viper Strike and Poison Attack can kill Invoker easily if Ghost Walk is on cooldown.

* Heroes with illusion and clone abilities may confuse Bloodseeker, causing him to waste time in fights: Phantom Lancer, Chaos Knight, Arc Warden

* Heroes that can slow Charge of Darkness by a huge amount: Venomancer, Viper, Dazzle, Arc WardenLion

* Corrosive Skin gives Viper additional resistance to Phoenix's magical damage, and since they deal damage over time, Phoenix would be constantly afflicted by his passive's own debuff, making him not an ideal target for Phoenix's harassment. Phoenix's abilities also constantly drain its own health away, becoming more vulnerable to Poison Attack.

* Most of Magnus' abilities except Empower will trigger damage through Corrosive Skin.
* Poison Attack and Viper Strike can slow Magnus during Skewer, as well as putting his Blink Dagger on cooldown, preventing him from initiating or re-initiating.

* Aside from his ultimate, Lifestealer has no AoE abilities to deal with Phantom Lancer's illusions, nor does he have the mobility to escape Phantom Rush.
* Doppelganger dispels Open Wounds.
* Phantom Lancer usually builds Diffusal Blade, which a problem for a low already mana hero like Lifestealer.
Additional:
* Lifestealer has no way of dealing with Phantom Lancer's illusions.
* Phantom Lancer also commonly builds Diffusal Blade, which poses a large problem to Lifestealer and his low mana pool.

* Heroes who can easily harass Crystal Maiden out of lane in the early game (Clinkz, Viper) can prevent Crystal Maiden from being able to level effectively, and can ultimately slow down her level 6, 12, and 18 to a point where enemy carries already have items to address her ultimate.

* Poison Attack and Viper Strike allowing to kite and slow Earthshaker significally, putting Blink Dagger on cooldown and preventing him from initiating or re-initiating.
* Nethertoxin breaks Aftershock. The silence from Level 25 talent also prevents Earthshaker from initiating or re-initiating.
Additional:
* Being a melee hero, Earthshaker's movement is liable to suppression by Poison Attack and Viper Strike.
* Earthshaker's kit, with the exception of Enchant Totem, deals magic damage. Corrosive Skin effectively blunts his killing potential with a standard Blink combo among other things.
* Nethertoxin disables Aftershock, which removes the stun and bonus damage from Enchant Totem and Echo Slam.

* Nethertoxin prevents the lifesteal from Ransack.
* Meepo and his clones have a lack of magic resistance, so they're vulnerable to Poison Attack & Viper Strike directed onto one clone.

* Nethertoxin cancels out Kraken Shell and stops the hard dispel from passively activating, preventing Tidehunter from functioning as a frontline tank.
* Anchor Smash is mostly irrelevant against a ranged hero.
* Tidehunter relies on the threat of Ravage, which has an obscenely long cooldown. Viper can exploit the downtime with his short cooldowns.