* 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.

* Any hero with low mobility and max healthsuch as Silencer, Crystal Maiden etc.

* 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.
Additional:
* 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.

* While Broodmother can hide in the trees with Spin Web, Primal Beast's ability to trample trees down can give him an edge in catching her.
* Insatiable Hunger will not do much vs Primal Beast's onslaught of disables.
* While Silken Bola can slow Primal Beast down, it's not enough to stop Trample from doing more damage than Broodmother can do back.
* Spawn Spiderlings will be destroyed by Onslaught and Trample very easily.

* 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.

* Any hero with low mobility and max healthsuch as Silencer, Crystal Maiden etc.

* Quill Spray and Bristleback harass Luna more efficiently than she does with Lucent Beam.
* Bristleback helps return a lot of damage to Luna’s team if she uses her nukes on him and he has his back to her.
* Viscous Nasal Goo and Warpath are enough to outrun a speedy Luna.
* Bristleback tends to be a frequent carrier of Crimson Guard and Eternal Shroud, which are good protection from Moon Glaives and Eclipse.
* For the same reasons, Bristleback makes a very powerful ally for Luna when they are in the same team.

* Any hero who lanes very poorly will struggle with Primal Beast's potential snowball in the very early levels, like Keeper of the Light, Luna, Templar Assassin...

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

* Sprout gets destroyed by Trample and Onslaught.

* Quill Spray quickly destroys Chaos Knight's Phantasms.

* Illusion heroes will struggle against Primal Beast's area damage capability, such as Chaos Knight, Naga Siren, Terrorblade.

* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: Tidehunter, Bristleback, Slardar.

* Hard carries who just want to farm and be left alone will not appreciate Primal Beast, heroes such as Medusa, Drow Ranger...

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

* Special mention to Lifestealer who can use Rage to prevent Trample damage, but Primal Beast's ultimate can still be casted during the spell.

* Tiny's nonexistent armor in the early game makes him very vulnerable to Quill Spray's large amounts of physical damage.
* Bristleback decreases Tiny's high burst damage against Bristleback.
* Viscous Nasal Goo can slow Tiny to a crawl and allows Bristleback to easily kite him with his high movement speed and Quill Spray's long range, as Tiny has no ability to escape.

* Rubick deals little damage on his own, and Bristleback can simply shrug off all his spells and chase Rubick down with his Quill Spray and the damage bonus from Warpath.
* Rubick does not tend to charge forward in teamfights, stay in the front lines under most circumstances, yet effective casts of Quill Spray and Viscous Nasal Goo requires the opposite as they require multiple casts and close range to add up stacks.
* Rubick does not benefit from Warpath through casting the stolen spell.
Additional:
* Bristleback's abilities are nearly useless for Rubick to Spell Steal, as he does not gain the bonuses from Warpath.

* Phantom Assassin is known to be weak against bursts of magical damage, something Primal Beast excels at from the beginning of the game. He can use this to his advantage by constantly hunting Phantom Assassin down, especially if she is left alone to farm.
* Primal Beast is a good carrier of Ethereal Blade, Vanguard and Shiva's Guard all of which are very good against Coup de Grace and Phantom Strike.
* Even though Primal Beast does a lot of physical damage early on, later once Blur becomes more potent, she may find herself being overwhelmed by Trample and Onslaught instead.
* Primal Beast's ultimate goes through spell immunity and his level 25 talent makes it even more devistating against Phantom Assassin.

* Morphling relies on Attribute Shift (Agility Gain) to take last-hits. Primal Beast's burst damage ability can constantly threaten Morphling, especially due to his short attack range. If forced to escape with Waveform, Primal Beast can catch up with Onslaught.

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

* Magnus is not tanky and struggles against burst damage, something Primal Beast excels at in the early-to-mid game. Primal Beast is also able to out-damage Magnus's Empower and can even contribute to his Uproar stacks.
* Using Skewer to drag Primal Beast while he is trampling will count as movement and will trigger a rapid number of slams, which could prove lethal to Magnus.

* Pudge is particularly susceptible to Bristleback's Viscous Nasal Goo and Quill Spray due to his naturally low armor and 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.
Additional:
* 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.

* Focus Fire potentially trigger with Quill Spray very harassing and passive abilities from Bristleback Bristleback and Warpath stacked damage. Additionally,Combination Quill Spray and Blade Mail is very possible kill her's since Windranger's activated Focus Fire. At the same time,Windrun does not protect from Quill Spray.
* Bristleback's tanky in late game build Heart of Tarrasque and Vanguard until upgrade Crimson Guard or Abyssal Blade is very difficult for Windranger's kill Bristleback and her can need more damage.
* Spamming Viscous Nasal Goo is very harder Windranger's Windrun movement speed. Bristleback combinating build Assault Cuirass also render Windranger's loss armor.
* Bristleback must build Lotus Orb cause make reflects Windranger's target hard Shackleshot and Focus Fire.
Additional:
* Combo Quill Spray and items Blade Mail can easily trigger from Focus Fire damage.

* Primal Beast can use Uproar to tank a portion of Omnislash, giving him an edge in surviving it. Primal Beast can also dash away after Omnislash with Onslaught, disallowing Juggernaut from any follow-ups.
* Blade Fury will never do more damage than Uproar once the stacks are activated.
* Primal Beast is very commonly buying items that are good against Juggernaut, such as Ethereal Blade and Heart of Tarrasque.
* Primal Beast has one of the few ultimates that can prevent Juggernaut from spinning away with a teleport.

* Pierce the Veil does not prevent Primal Beast from using any of his spells to their fullest and is one of the few heroes that can disable her during her ultimate and a common Black King Bar purchase.
* Gunslinger will be disabled if Primal Beast buys an Aghanim's Scepter.

* Primal Beast has multiple ways to cancel Life Drain very quickly.
* Pugna has a very low strength gain and as a support does not have much gold to buy health items, making him vulnerable to Primal Beast's onslaught of magical damage.
* Ironically, Decrepify actually just increases Primal Beast's damage on the targeted ally if Trample is activated. However, it can be used to slow him down and prevent any further Trample damage.

* 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.

* 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.
Additional:
* 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.

* 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 can still get 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.

* 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.

* 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:
* 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 quickly 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.

* 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.

* Dispersion reduces damage based on a percentage, which is very minimal against large amounts of small instances of damage such as Trample. It reduces each tick by about 14 at the maximum level, which is very small.
* Desolate is never a threat to Primal Beast due to his large health pool and Uproar is still out-damaging the ability.
* Onslaught can allow Primal Beast to chase Spectre fleeing with Spectral Dagger, as both skills phase through trees and terrain.
* Primal Beast can also dispel Spectral Dagger's slow with his left level 15 talent, making it completely useless against him.
* Primal Beast excels at early aggression, pushing weak carries out of lane and farming areas he wants to control. Overall just not a pleasant

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

* Axe, Bristleback, Centaur Warrunner, Spirit Breaker, Pudge, Huskar, Wraith King: 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.

* Heroes who have low or high armor but very high health will be difficult for drow to burst down quickly: Primal Beast, Axe, Centaur Warrunner.

* Heroes who have high health are a problem for Sniper because he likes to attack the closest target and sit at the back, much like a Terrorblade so when that hero doesn't die; he's forced to show his position for a very long time: Centaur Warrunner, Legion Commander, Primal Beast.

Additional:
* Primal Beast is one of Sniper's greatest counters, as he has no real means of escape and is very squishy, especially in the early game. Sniper's potshots and Shrapnel can contribute to Primal Beast's Uproar and further make him tankier than he already is. Onslaught allows him to close the gap on Sniper at his own volition, and Trample can deal serious damage to his meager health pool.

* Any hero who lanes very poorly will struggle with Primal Beast's potential snowball in the very early levels, like Keeper of the Light, Luna, Templar Assassin...

* Any hero who lanes very poorly will struggle with Primal Beast's potential snowball in the very early levels, like Keeper of the Light, Luna, Templar Assassin...

* Heroes who can stop Axe from getting close will severely inhibit his presence in fights: Bristleback, Crystal Maiden, Batrider, Arc Warden, Winter Wyvern, Clockwerk

* Long lockdown is a great way to deal with Axe to prevent Berserker's Call from being used, heroes such as Legion Commander, Beastmaster and Primal Beast are good examples of this.

Additional:
* Berserker's Call will be a stun for Primal Beast and not much else due to Trample making him unable to attack.
* Battle Hunger is neglitable because Primal Beast has a much bigger health than Axe, so he does not need to fear being slowed, or his other abilities including Counter Helix or even a Blade Mail.
* Getting Primal Beast low enough to use a successful Culling Blade can be very difficult due to his massive health advantage over most heroes.
* Not ability related but Primal Beast does not need to fear Axe in lane, as Trample, combined with Uproar and Onslaught will do a ton of damage even if Axe has a Vanguard.

* Heroes who cannot escape from Trample early might be easy first blood. Heroes like Witch Doctor and Omniknight should play very cautiously alone...

* Heroes who can continue dealing damage even while being stunned: Luna, Razor, Axe, Bristleback, Leshrac, Death Prophet.

* Durable heroes: Axe, Dawnbreaker, Bristleback, Tidehunter, Wraith King, Primal Beast, Underlord.

* 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 easily allow Bristleback to turn his back in order to proc Bristleback continuously and to massively reduce to damage dealt to him: Arc Warden, Venomancer, Luna.

* Illusion heroes will struggle against Primal Beast's area damage capability, such as Chaos Knight, Naga Siren, Terrorblade.

* Heroes with unorthodox escapes will struggle against Primal Beast, such as Nature's Prophet, Tinker, and Templar Assassin.

* Heroes who cannot escape from Trample early might be easy first blood. Heroes like Witch Doctor and Omniknight should play very cautiously alone...

* Heroes with damage-over-time abilities easily allow Bristleback to turn his back in order to proc Bristleback continuously and to massively reduce to damage dealt to him: Arc Warden, Venomancer, Luna.

Additional:
* Arc Warden has relatively lower armor and mobility, which makes him an easy target to apply Quill Spray and Viscous Nasal Goo stacks.
* Arc Warden also does not like to build a Silver Edge as it takes a long time to build up and may slow down the timings for other important items needed in the game like Gleipnir.
* However, do note that in a game where Arc Warden's team has many jumping capabilities or good passives, like a Tidehunter or Spectre, a Silver Edge becomes incredibly valuable on Arc Warden as not only can he run away from the jumps, he effectively gets 2 breaks, and Bristleback may not be the best pick.

* 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.

* Since Primal Beast is highly mobile with Onslaught alone, he will be difficult to catch with both Cold Feet and Ice Blast.
* Ice Blast is less effective due to Primal Beast's massive health pool and resistance to taking damage.
* While Chilling Touch can be used to slow Primal Beast briefly, it is not enough to beat him back, and can also contribute to his Uproar stacks.
* Primal Beast has a dispel talent at level 15 that will remove Cold Feet immediately when Uproar is used.

* 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

* Heroes with abilities that can lock down Terrorblade and prevent him from using Sunder: Bane, Batrider, Earthshaker, Elder Titan, Faceless Void, Invoker, Legion Commander, Mars, Primal Beast, Riki, Shadow Shaman, Silencer, Vengeful Spirit, Void Spirit.

Additional:
* Terrorblade has no stun and is vulnerable to Primal Beast's spell comboes due to his low health points in the laning stage and mid game.
* Reflection can be dispelled using Primal Beast's level 15 left talent.
* Sunder is the only real threat Terrorblade has against Primal Beast but he may die before he can even use it.

* Onslaught prevents all of Razor's abilities from being effective against him, especially in the laning stage.

* Bristleback's constant harass from Quill Spray will greatly hurt Enigma's laning and kill his Eidolons.
* However, Bristleback has no way of canceling Black Hole at all. And Bristleback is not a hero that goes for disabling items to counter that problem.

* Dark Pact, Shadow Dance and Depth Shroud will do nothing against Onslaught and Trample, as they are both ground area-of-effect spells.
* Primal Beast has a gigantic hitbox, which could be difficult for Slark to escape with Pounce should Primal Beast choose to block him. Pounce also does not completely prevent Primal Beast from trampling offensively, as he still has some room to move.
* Primal Beast has a huge health pool making it difficult to shed it with Essence Shift and may llow Primal Beast to build Uproar stacks against him very rapidly.

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

* 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.