* Essence Shift allows Slark to hit bristleback freely whether on the front or back, stealing attributes and make bristleback much less tanky.
* Pounce can be used to disengage and recover loss HP with his ultimate passive, and can return to fight in a short period while bristleback is already injured and got some of his attributes stolen.
* Dark Pact makes it near impossible to keep Viscous Nasal Goo debuff on slark.
* Although Dark Pact cannot dispel Quill Spray, means Slark will still receive quill stack damage even if he uses Shadow Dance before.
* Slark builds Silver Edge in almost every game, an item that greatly counter birstleback.

* Shadow Dance allows Slark to not be targeted by Unstable Concoction, making Alchemist stun himself and making himself vulnerable to the enemy.
* Dark Pact also allows him to just purge off the stun if timed correctly.
* Essence Shift will steal stats over long durations at a time should Alchemist lack the damage to kill Slark.

* Corrosive Haze followed by Slithereen Crush takes advantage of Alchemist's main weakness, being physical damage before he has the change to improve his surviability with items.
* Bash of the Deep will deal lots of damage during the laning phase.

* Guardian Sprint allows Slardar to outrun Bristleback, even when slowed by Viscous Nasal Goo.
* Corrosive Haze's armor reduction makes Bristleback much less tanky.

* Eye of the Storm melts Bristleback's armor, and makes him much less tanky.
* Static Link can completely drain Bristleback's bonus damage from Warpath.
Additional:
* Eye of the Storm melts Bristleback's armor, and makes him much less tanky.
* Static Link can completely drain Bristleback's bonus damage from Warpath.
* Storm Surge allows Razor to outdistance Bristleback, even with a few stacks of Viscous Nasal Goo on him, Also, if Razor has his Shard, but Bristalback does not, Viscous Nasal Goo will deal damage to Bristalback every time he uses it, And normally, it won't be affected by Bristlebacks Passive, as Bristleback will face him to cast it.

* Alchemist's reliance on fast attack speed to do single-target damage makes him vulnerable to Static Link. It also goes through Black King Bar, which is a standard item on Alchemist.
* Eye of the Storm is great against high health strength heroes as it reduces their survivability to physical damage.
* Razor has early lane push to counter Acid Spray.

* Heroes that withstand damage like Timbersaw, Bristleback, Dragon Knight and others will have their durability largely reduced when hit by an Ice Blast due to the risk of shattering.

* Ice Blast nullifies the health regeneration granted by Chemical Rage, which Alchemist greatly relies on to stay alive in battle.
* Alchemist tends to build Armlet of Mordiggian which can be deadly during Ice Blast.
Additional:
* Ice Blast cancels out Chemical Rage's rapid health regeneration. It can also take advantage of Alchemist's Armlet of Mordiggian toggling, as it will make HP drain insanely fast, essentially killing the bearer in no time.

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

* 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.

* Alchemist is a well-known Radiance carrier among other auras your illusions will benefit from. They also get the extra move speed and reduced base attack time from his Chemical Rage, and it's even better if you can catch him as his own rage is about to expire.
* Disruption will buy enough time for all allies to retreat when Alchemist starts to activate Unstable Concoction.

* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Once you have an Aghanim's Scepter, Shadow Demon instantly reaches a new power spike and becomes a counter for a variety of heroes that have strong passives.
* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* You can always stack camps and farm the scepter with Shadow Poison.

* Reaper's Scythe can kill Alchemist before Chemical Rage has the time to heal him.
* Ghost Shroud can prevent Alchemist from attacking Necrophos, as well as make him immune to Acid Spray and Unstable Concoction damage.
* Heartstopper Aura will do damage as long as Necrophos is alive based on health percentage, which is a problem for a strength hero such as Alchemist.

* Heartstopper Aura deals percentage-based damage flagged as HP removal, so it is not reduced by Bristleback, nor does it trigger passive Quill Sprays.
* Reaper's Scythe is very effective against Bristleback not only due to its percentage-based damage, but rather because it first stuns and then deals its damage, allowing Necrophos to position in front of Bristleback in time.
Additional:
* Reaper's Scythe and Heartstopper Aura deal percentage-based damage, ignoring Bristleback's high health.
* Heartstopper Aura's HP removal does not trigger Bristleback's passive.

* Bristleback will not be able to cast Viscous Nasal Goo or Quill Spray while silenced, effectively blocking a major part of the hero's damage and preventing Warpath charges from stacking.
* Arcane Curse slows Bristleback down and lasts longer the more abilities he uses. On the other hand, if he doesn't use any abilities, he will begin to lose Warpath charges.
Additional:
* Arcane Curse stacks every time Bristleback uses an ability, forcing him to stop spamming his abilities, or take heavy health degeneration.
* Glaives of Wisdom steals intelligence both permanently and temporarily, causing mana issues for Bristleback.
* Last Word and Global Silence stops Bristleback from using his abilities altogether.

* Mana Break quickly eats away at Bristleback's small mana pool, preventing him from spamming Viscous Nasal Goo and Quill Sprays.
* Bristleback has no innate mobility. Bristleback is easily kited by Blink, ignoring the protection from Bristleback.
Additional:
* Mana Break removes both a percentage and flat amount of your mana, preventing you from using abilities in the lane.
* Blink Anti-Mage has very high mobility with this skill, and can easily escape from you since you have no way to prevent his blink. He can also use this offensively to get in front of you during fights.

* Duel makes Bristleback fight Legion Commander face to face, forcing him to take full damage.
* Press the Attack dispels the slow from stacks of Viscous Nasal Goo.
Additional:
* When dueled, Bristleback will have to face Legion head on, not allowing his passive Bristleback to come into effect.

* Skywrath Mage can easily harass Alchemist in the laning phase with multiple Arcane Bolts. Additionally, if Alchemist is in the process of throwing an Unstable Concoction, and has no way to dispel Ancient Seal, the self stun becomes an easy set up for Mystic Flare.
* Caution, however, as a decently farmed Alchemist with {Item ID:Radiance} and {Item ID:Manta Style} can easily send illusions to harass and force Skywrath Mage out.

* Shukuchi gets Weaver in front of Bristleback, negating the protection from the Bristleback passive.
* Weaver's mana break talent depletes Bristleback's mana pool, preventing him from spamming abilities.

* Time Dilation while Quill Spray and Viscous Nasal Goo are on cooldown will make these abilities unusable for a long time, rendering Bristleback nearly useless.
* Bristleback cannot turn inside the Chronosphere, which makes it easy to attack him from the front, completely bypassing his passive damage reduction.
Additional:
* Time Dilation prevents Bristleback from spamming his low-cooldown abilities, greatly reducing his damage and effectiveness.
* Chronosphere allows allies to reposition and hit Bristleback from the front, bypassing his defensive bonus from behind.
* Bristleback has no way to prevent Void from using Time Walk.

* Ember's magic damage build is able to burst down Alchemist due to his low strength gain and Alchemist's normal item pick up.

* Quas-Exort Invoker can win the mid lane easily against Alchemist because Quas regeneration will nullify Acid Spray's damage over time and Exort damage bonus will allow Invoker to out last hit Alchemist.

* Axe can force Alchemist to attack him with Berserker's Call. High attack speed from Chemical Rage will cause Counter Helix to proc multiple times.
* This can get worse if axe has Blade Mail, which then returns all damage to Alchemist himself.
* Axe's abilities can pierce through Black King Bar, which is a common item for Alchemist.
* Berserker's Call grants Axe a huge bonus armor, which greatly counters Alchemist's physical damage for the most part.

* Axe forces Bristleback to turn around with Berserker's Call, allowing allies to attack him without fear of his passive.

* Sharpshooter deals massive damage to Bristleback and applies a high duration disable on his passive.
* Bushwhack and Scurry can be used to easily kite Bristleback.
Additional:
* Bristleback and Warpath can be disabled by Hoodwink's Sharpshooter ability for a long period of time, reducing his both offense and defense.
* Scurry and Bushwhack can be used to kite bristleback.

* Tidebringer will deal lots of damage to Alchemist before he builds physical survivability items.
* Torrent and X Marks the Spot can control Alchemist at all stages of the game before he has Black King Bar.
* Ghostship's rum buff will greatly reduce the Alchemist's damage output in teamfights including his Radiance.

* Mana Drain is a headache for Bristleback to deal with during the laning stage, as it denies him the ability to get last hits with Quill Spray.
* Finger of Death deals high damage to Bristleback, and only triggers his passive once.

* Phantom's Embrace silences Viscous Nasal Goo and Quill Spray.
* Ink Swell stuns Bristleback and gets allies in position faster with increased movement speed to attack his front, countering his passive ability.

* Whirling Death deals damage as well while reducing 15% of Bristleback's strength, which reduces Bristleback's tankiness.
* Reactive Armor can sustain through multiple Viscous Nasal Goo and Quill Spray stacks.
* Timber Chain makes it hard for Bristleback to slow down Timbersaw with Viscous Nasal Goo.

* Untouchable greatly reduces Chemical Rage's attack speed advantage.

* Visage can quickly kill heroes with low to medium base armor and no innate escape mechanism. Examples include Alchemist, Crystal Maiden and Zeus.

* Heroes without an escape mechanism: Shadow Fiend, Alchemist

Additional:
* Chemical Rage will rarely save Alchemist against Ursa's Fury Swipes.
* Enrage allows Ursa to both be a threat to Alchemist and avoid his over time damage.

* Clinkz can use Burning Army in teamfights which will cause a problem for Alchemist.

* In general, attacks of the melee heroes who are entirely reliant on dealing physical damage and/or have very little to no area-of-effect abilities will make Underlord tickle and will have no effect against him, and will be unable to ambush Underlord and his team if Underlord chooses to use Dark Rift to get to a designated point of the map: Phantom Assassin, Terrorblade, Troll Warlord, Drow Ranger, Phantom Lancer, Chaos Knight, Sven, Wraith King, Bounty Hunter, Alchemist, Templar Assassin, Nyx Assassin, Bane.

* Tanky melee heroes that can easily be kited, which allows Outworld Destroyer to deal heavy damage with Arcane Orb from a distance: Sven, Underlord, Bristleback.

Additional:
* Sanity's Eclipse only triggers Bristleback's passive once, and deals high damage against Bristleback's low intelligence.
* Outworld Destroyer's high burst damage is not negated by Bristleback's passive, So even if Bristleback turns his back on Outworld, Outworld Destroyer can decimate Bristleback quickly,
* If Bristleback attempts to flee, or tries to close the gap, Outworld can banish him with Astral Imprisonment, both reducing Bristlebacks much needed mana, and allowing Outworld to move in front of him, forcing him to take the full damage from his spells, This will also allow Outworld to land a devasting Sanity's Eclipse, without it being reduced by Bristleback's passive,

* Heroes who rely on skills to become a heavy hitter in a certain amount of time can waste their timing because of a lucky Lucky Shot's disarm: Terrorblade, Sven, Clinkz, Windranger, Alchemist, Dragon Knight, Legion Commander

* Heroes who deal single instance burst damage will only proc Bristleback once: Lina, Lion.

* Batrider's turn rate slow from Sticky Napalm makes it harder for Bristleback to keep his back towards the enemy.

* Terrorblade's Sunder is not affected by the Bristleback damage reduction.

* Pugna's Decrepify makes sure that either Alchemist is unable to hit anyone while also being slowed and susceptible to magical damage, or can protect an ally from physical attacks. Besides, Pugna can push early on, when Alchemist is not strong enough to repel it, so by the time Alchemist comes online, he might be forced to sit in base.

* Feast is good against high health strength heroes such as Alchemist.
* Rage allows Lifestealer to not be targetable by Unstable Concoction, possibly making Alchemist stun himself.

* Alchemist has very bad armor and does not build armor items for the large majority of his build, so Jingu Mastery and Wukong's Command can be very deadly.
* Desolator, Sange and Yasha or Diffusal Blade can all be purchased to increase your damage against Alchemist or just to keep your movement speed high enough to match him while Chemical Rage is active.
* Monkey King is an agility hero and scales with armor, so Acid Spray loses it's effectiveness later in the game.