* Lycan's wolves deal little damage to Bristleback, and are easily killed by Quill Spray, even when they're invisible.
* Lycan's lack of burst damage makes it very hard for him to kill Bristleback, especially when his back is turned.
Additional:
* Quill Spray can be used to kill Lycan's summons.
* Bristleback allows him to stay alive against Lycan while dishing out counter attacks
* He can overpower Lycan with his Warpath instead.

* Her Mana Shield is too tough for Lycan to break in.
* Mystic Snake can hit for a massive damage once it spread between his summons.
Additional:
* Can be easily petrified despite his speed.
* Summoned wolves will be targeted by Split Shot or Mystic Snake

* Quill Spray usually hits Meepo's clones, although Bristleback cannot turn his back when rooted with Earthbind.

* Poof won't damage Medusa and he can Gaze an entire flock of Meepos.
* Mystic Snake will easily become the bane of Meepo early game.

* Bristleback's tankiness can enable him to chase Enigma out of a teamfight, making it difficult to initiate with a Black Hole.

* Medusa's Split Shot can make quick work of Enigma's Eidolons and take advantage of their considerable bounty.
* If Medusa activates Stone Gaze at the start of a fight, it can make initiating — and landing an effective Black Hole exceedingly difficult.
* Mystic Snake can be potentially detrimental to Enigma's initiation. Getting hit by the latter high-damage bounces (from standing behind his Eidolons or his teammates) can hinder his mana pool, preventing him from executing a strong initiation.
Additional:
* Mana Shield makes Medusa harder to kill with Enigma's Black Hole and Pulse combo.
* Medusa's Split Shot can kill Demonic Conversion creeps easier and Mystic Snake bounces off from them.
* Stone Gaze makes it hard for Enigma to approach Medusa for a Black Hole.

* Lifestealer's low mobility makes him easy to kite.
* Stone Gaze pierces Rage, wasting its cooldown and making Lifestealer unable to fight.

* Heroes with high physical damage can damage Lifestealer more than he can heal: Bristleback, Clinkz, Luna,Shadow Fiend, Slardar

* Heroes who continue dealing damage while being stunned: Luna, Razor, Axe, Bristleback, Leshrac,

* If Medusa activates Stone Gaze, the charge will inevitably fail.
* Mana Shield and overall tankiness allows Medusa to easily survive Spirit Breaker's initiation.

* Enchantress often has a small army of neutral creeps, allowing Medusa to hit her with a later bounce of her Mystic Snake.
* Untouchable is ignored by secondary attacks from Split Shot.

* Bristleback is one of the hardest heroes to gank with a Meat Hook and Dismember combo, and attempts to do so sometimes backfire on Pudge.
Additional:
* Pudge is particularly susceptible to Bristleback's Viscous Nasal Goo and Quill Spray due to his naturally low armor & poor agility gain.
* Bristleback, in combination with his strength gain, high health, common itemization for magic resistance and damage reduction from Bristleback makes him a poor target for Pudge.

* Bristleback decreases Tiny's high burst damage against Bristleback.
* Tiny's high damage will also proc Bristleback multiple times.
* Viscous Nasal Goo can help counteract the bonus armor granted by Grow.

* Split Shot will keep attacking Pangolier even when he is rolling around.
* Stone Gaze stuns Pangolier during Rolling Thunder, or forces him to roll away.

* Viscous Nasal Goo slows down Dragon Knight and lowers armor, locking him down and making him more vulnerable.

* Quill Spray will hit Sand King inside Sand Storm, damaging him and putting Sand King's Blink Dagger on cooldown, preventing him from escaping.
* Epicenter's numerous damage ticks will trigger Bristleback's passive repeatedly during teamfights.

* Macropyre's frequent damage ticks causes Bristleback to activate repeatedly, resulting in free damage as long as Bristleback faces away from Jakiro.

* Quill Spray's constant AoE damage will hit Dark Willow even in Shadow Realm. Its automatic damage will hurt her if she tries to get close and use Bedlam.

* Mystic Snake can harass Axe in lane and drain his small mana pool.
* Mana Shield reduces the effectiveness of Counter Helix.
* Stone Gaze makes it very difficult for Axe to pursue.

* Heroes who can slow and kite Axe will severely inhibit his presence in fights: Bristleback, Crystal Maiden, Batrider, Arc Warden, Winter Wyvern, Clockwerk

* Quill Spray is very effective against Io, as it has very low armor and has to stay close to the fight to not break its Tether.

* Fortune's End cannot dispel Warpath stacks on Bristleback or Quill Spray stacks on allies.
* Bristleback can heavily reduce Oracle's damage output. With it, Oracle may accidentally heal Bristleback with Purifying Flames, especially if Bristleback has bonus magic resistance.

* Quill Spray and Bristleback harass Luna more efficiently than she does with Lucent Beam.
* Bristleback withstands Luna’s nukes, and gives lots of damage in return.
* Viscous Nasal Goo and Warpath are enough to outrun a speedy Luna.
* Bristleback tends to be a frequent carrier of Crimson Guard, which is good protection from bouncing glaives.
Additional:
* Multiple instances of damage from Eclipse will trigger Bristleback's passive repeatedly in a short time, dealing tremendous damage to Luna and her teammates.
* Luna's damage burst may be high, but it will not be enough for her to take down Bristleback.

* Bristleback's tankiness and Bristleback allow him to outlast Burning Spears' damage-over-time at almost any point in the game. In addition, if Huskar chooses to cast Life Break on Bristleback, Bristleback can simply turn around before it hits and receive little damage.
* Viscous Nasal Goo will reduce Huskar's low armor even further, and Quill Spray and Warpath will tear him down extremely quickly.
Additional:
* The damage from Burning Spear can be reduced by turning away from Huskar.
* Bristleback can bait Huskar into using Life Break on him, then turn around and receive very little damage.

* Viscous Nasal Goo can hinder Crystal Maiden's already abysmal mobility, which allows Bristleback (or his teammates) to run her down and kill her.
* Bristleback frequently builds Blade Mail, which can quickly kill Crystal Maiden if her ultimate is used while he is under its effect.
* The passive part of Bristleback will trigger many, many times under the damage from Freezing Field, and as the stacks increase, the damage output from each successive cast (or proc) will eat away at Crystal Maiden's small HP pool.

* Lone Druid and The Spirit Bear cannot burst down Bristleback due to Bristleback
* Bristleback can easily run to Lone Druid without any hesitation, with Viscous Nasal Goo to reduce armor and slow the Spirit Bear or Lone Druid and Quill Spray can deal damage to both Lone Druid and the Spirit Bear at the same time

* Summoned gargoyles will give Medusa free target practice.
* Mana Shield will resist Soul Assumption instances without effort.

* Stone Gaze allows Medusa to easily kite and kill Sven.
* Mystic Snake eats away at Sven's small mana pool.
* Mana Shield negates much of Sven's burst damage.

* Quill Spray quickly destroys Chaos Knight's Phantasms.

* Mana Shield makes it very difficult for Bloodseeker to gain his Thirst bonuses.
* Rupture rarely kills Medusa through Mana Shield.

* Heroes that have AoE damage: Lina, Keeper of the Light, Timbersaw, Leshrac, Bristleback, Axe

* Bristleback, Centaur Warrunner, Spirit Breaker, Pudge, Huskar: These heroes are too tanky for Puck to burst down. Also, all of them have spells which can deal with and shut Puck down reliably.

* Bristleback's Viscous Nasal Goo can catch and slow Bounty Hunter. Warpath and Quill Spray can defeat him quickly due to his small HP pool when compared to Bristleback's.

* Heroes with damage-over-time abilities will not only proc Bristleback's passive continuously, they will also do little harm to him when he is facing away from the source: Venomancer, Arc Warden

* Heroes with cleave abilities and area of effect damage can make quick work of Chen's converted creeps and at same time gain farm: Magnus, Jakiro, Shadow Fiend, Kunkka, Luna, Dragon Knight, Medusa, Alchemist.

* Enemies that possess high defenses through magic resistance, damage reduction, or high regeneration will make it difficult to whittle their health down to get to Reaper's Scythe's threshold. Such heroes include Bristleback (although only from behind), Spectre, Ursa, and Dragon Knight.

* Mana Shield tanks most of the damage from Reaper's Scythe; with sufficient mana, the kill threshold drops to 15%/17%/19% health (before reductions).
* Heartstopper Aura does not chip away at Medusa's mana, this makes it not a threat as it deals damage based on current health.
* Necrophos has a movement speed equal to Medusa, and is easy to chase down with a slowing item in Medusa's inventory.

* Heroes with Linken's Sphere as core item: Weaver, Morphling, Medusa.

* Stone Gaze negates Dispersion's damage reduction and allows Medusa to kite Spectre.
* Spectre's small mana pool is depleted quickly by Mystic Snake.
* Split Shot can clear Haunt illusions quickly.

* Bristleback's tankiness and damage reduction from the rear makes him very hard for Phantom Lancer to chase and finish off, due to his lack of burst damage.
* Quill Spray destroys Phantom Lancer's illusions.
* Bristleback's passive costs no mana, meaning that it will continue to trigger even if Phantom Lancer drains Bristleback's mana with Diffusal Blade.
Additional:
* Quill Spray cleans up Phantom Lancer's illusions in no time.
* Phantom Lancer's complete lack of burst damage makes it nearly impossible for him to kill Bristleback during chases.

* Bristleback's abilities are nearly useless for Rubick to Spell Steal, as he does not gain the bonuses from Warpath.
Additional:
* Rubick deals little damage on his own, so Bristleback can simply shrug off all his spells and chase you down with his spells and attacks.
* Quill Spray requires multiple casts and close range to add up stacks. Because Rubick does not stay in the front lines, it's generally not a good spell for him to steal.
* Viscous Nasal Goo will slow Rubick down even further and reduce his armor, making him vulnerable to Quill Spray and the damage bonus from Warpath.

* Doom does not disable Mana Shield. As such, Doom's damage is largely mitigated by her mana shield. Additionally, Medusa is not reliant on her abilities to be effective during a teamfight, making Medusa an unproductive hero to target.
* Medusa is an ideal Linken's Sphere carrier. Should one be purchased, and without any additional disables, Doom may find that few opportunities exist to effectively lockdown, disable, and kill Medusa.

* Mana Shield makes Medusa very hard to take down in Duels.
* Stone Gaze stops Legion Commander from Dueling altogether, regardless of who she targets.

* The bonus Backstab damage from Cloak and Dagger is rendered irrelevant with Bristleback and hurts Riki more than him because of the passive Quill Spray.
* Riki still gets damaged by Bristleback's Quill Spray while invisible, and it can be hard to deal with in lane.
* Bristleback is not too bothered by Smoke Screen. Though he cannot use Quill Spray manually inside it, it still procs passively when he takes damage from the back. The movement speed from Warpath allows him to get out of the area easily.
* Due to Bristleback's natural tankiness, he is an ideal Gem of True Sight carrier.
* Riki rarely buys Silver Edge to break Bristleback's passive because the invisibility aspect of it is redundant.
Additional:
* Quill Spray will hit Riki even when he is invisible.
* Cloak and Dagger's bonus backstab damage is rendered irrelevant against Bristleback.
* Smoke Screen does not stop Bristleback's passive from activating.
* Due to Bristleback's natural tankiness, he is an ideal Gem of True Sight carrier, directly countering Riki's invisibility.

* Bristleback need not worry about charging into Magnetic Field, and quickly clearing up Arc Warden's summons and Tempest Double with Quill Spray.
Additional:
* Bristleback activates frequently while he escapes from Arc Warden's Necronomicon army.
* Arc Warden has little armor and mobility, which makes him an easy target to apply Quill Spray and Viscous Nasal Goo stacks.

* Split Shot can destroy Tombstone Zombies and Tombstone itself while still damaging heroes.
* Mana Shield reduces the impact of Decay and Flesh Golem's Plague Aura.

* Quill Spray destroys spiderlings, and hits Broodmother even when she's regenerating in her webs. This makes Bristleback one of her hardest counters in lane.
Additional:
* Bristleback reduces most of Broodmother's and her spiderlings' damage.
* Quill Spray will hit any spiders in its proximity, hindering Broodmother's fighting and farming capabilities.