Slardar
* 
Bloodseeker's 
Rupture forces Slardar to stay still during fights, preventing Slardar from using Guardian sprint to move in and out of fights. This takes away the ability to initiate and re-initiate with Slithereen Crush's low cooldown. Due to the increased move speed from Guardian Sprint, Slardar can lose health at about 160% the rate of normal heroes while under Rupture. Bloodseeker's 
Thirst also gives him enough move speed so that he's one of the few heroes who can outrun or catch up to a Slardar during Guardian Sprint.
Lycan
* Rupture completely negates Lycan's high mobility.
* All of Lycan's summons are good sources of healing with Bloodrage.
Additional:
* Rupture completely negates Lycan's high mobility.
* All of Lycan's summons are good sources of healing with 
Bloodrage.
Slardar
* Enigma can be a perfect counter-initiator with his ultimate. A perfectly timed Black Hole will turn the tide of any initiation, especially from heroes like; 
Spirit Breaker, 
Legion Commander, 
Axe, 
Puck, and 
Slardar.
Lycan
* Can cast 
Demonic Conversion on one of Lycan's Wolves, making this a numbers fight.
* 
Malefice will greatly reduce his ability to engage
* 
Midnight Pulse can steep an area making it harder for Lycan to engage in.
Slardar
* 
Tidehunter's 
Kraken Shell dispels Corrosive Haze and Bash of the Deep's stun if enough damage is taken. 
Anchor Smash and Kraken Shell's damage block also reduces Slardar's damage.
Lycan
* Kraken Shell grants him massive physical attack protection
* Anchor Smash will wipe the area, clearing Lycan's wolves.
Lycan
* Tidebringer's cleave will cripple any of his summons.
* Could potentially build Heaven's Halberd to cripple Lycan even more.
Additional:
* 
Tidebringer can be used to kill Lycan's summons.
* Can also build into 
Heaven's Halberd which will disable Lycan's auto attacks, crippling him even more.
Slardar
* 
Fortune's End applies a basic dispel which can be used to dispel Corrosive Haze, or even Slardar's own Guardian Sprint.
* 
False Promise is able to dispel Corrosive Haze and Slithereen Crush stun/slow from any allies Oracle chooses to cast it on.
* 
Fate's Edict can also be cast on Slardar to prevent him from proccing his Bash of the Deep.
Slardar
* Abaddon can cast 
Aphotic Shield on any of his allies to immediately dispel Corrosive Haze and/or the stun and the slow components of Slithereen Crush.
* All of Slardar's debuffs are also removed if Abaddon's 
Borrowed Time triggers.
Lycan
* Paralyzing cask bounces between him and his wolves, keeping him stunned for long amounts of time.
Slardar
* 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.
Lycan
* 
Arctic Burn allows Winter Wyvern to escape Lycan, even when he uses his ultimate.
* 
Splinter Blast is very effective in dealing with Lycan's summons.
* 
Cold Embrace saves allies from Lycan's raw physical damage and can buy allies enough time to turn the tide of battle.
* 
Winter's Curse stops Lycan in his tracks and is very effective because of his summons.
Additional:
* All of Lycan's damage is physical which is totally negated by Cold Embrace.
* Lycan often moves around with large amount of creeps, wolves created by 
Summon Wolves and neutral creep dominated by 
Helm of the Dominator which can be easily cleared by Splinter Blast or used as a great source of damage by Winter's Curse. If you catch Lycan with creeps nearby and affected by 
Shapeshift using Winter's Curse on him will most certainly end up with his death.
Lycan
* A well landed 
Fissure can potentially take Lycan out of the fight for several seconds, who heavily relies on precious seconds from Black king bar and Shapeshift to fight.
* 
Aftershock reduces the effectiveness of his summons and can prove quite irritating for Lycan.
* 
Echo Slam is very powerful with the sheer amount of Lycan's units and will cause him to think twice when pushing towers.
Lycan
* 
Guardian Angel completely negates all of Lycan's damage since Lycan mainly deals physical damage.
* 
Purification can also be a problem for Lycan, as Purification deals damage around the target, which poses a problem for him and his summons.
Slardar
* 
Fire Spirits greatly reduces Slardar's already low starting attack speed (which Bash of the Deep relies on), making the laning phase very hard for him and discouraging Slardar from aggressively threatening lane kills.
* 
Supernova, ignoring Phoenix's lack of armor and Slardar's high damage single hits, is extremely hard for Slardar to take down on his own, especially after being hit by Fire Spirits.
* 
Icarus Dive is one of the longest distance escape spells in the game, and can help a good Phoenix escape from Slardar before he gets a 
Blink Dagger. However, the high cooldown means Phoenix is vulnerable to backstabs from any roamers after said spell is used.
* Slardar can interrupt an Icarus Dive from completing the flight with both of his stuns, however, likely leading to death if Supernova is on cooldown.
* A lot of the items a Phoenix builds throughout the game naturally counter Slardar. 
Shiva's Guard, Heaven's Halberd and 
Eul's Scepter of Divinity all stall Slardar's normal attacks in some way, while 
Spirit Vessel's percentage-based damage is good against his innate durability.
Lycan
* Brewmaster can waste a large portion of Lycan's ultimate by putting him in Cyclone.
* Lycan has no way to stop Brewmaster from using Primal Split by himself.
* Lycan's team often tries to push towers as a group, and Brewmaster excels at winning teamfights while trying to defend a tower.
Slardar
* 
Medusa cares less than other heroes about armor reduction, since 
Mana Shield blocks 70% of all damage without taking armor/magic resistance into consideration. This makes 60% of your Corrosive Haze ineffective until Medusa's mana is drained.
Lycan
* Her Mana Shield is too tough for Lycan to break.
* 
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
Slardar
* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: Tidehunter, 
Bristleback, Slardar.
Lycan
* 
Primal Roar allows Beastmaster to keep Lycan in place after he used his Shapeshift.
Lycan
* 
Great Cleave will kill Lycan's summons very rapidly.
* 
Warcry will allow Sven and his allies to tank Lycan's damage, which is mainly physical.
* 
Storm Hammer will damage and stun Lycan's as well as his summons.
Lycan
* All of Timbersaw's spells deal AoE damage, killing Lycan's summons very quickly.
* 
Reactive Armor will gain stacks quickly because of Lycan's summons.
Lycan
* Jakiro's area-of-effect abilities make him strong against heroes who rely on illusions and summons: 
Terrorblade, 
Naga Siren 
Chaos Knight, 
Phantom Lancer, 
Broodmother, 
Nature's Prophet, 
Lycan, 
Wraith King, 
Visage.
Lycan
* 
Pugna's 
Decrepify prevents the target from taking physical damage or doing damage, which poses a huge problem for Lycan, as he mainly deals physical damage.
Slardar
* Illusion heroes like the aforementioned Phantom Lancer or Naga Siren, or heroes that tend to buy Manta Style, like 
Luna or 
Juggernaut, will give Slardar a hard time, as his damage is single-targeted.
Lycan
* Heroes who rely heavily on melee attacks and lack early spell immunity are easily blocked and interrupted by Ink Swell: Lycan, 
Ursa, 
Troll Warlord.
Additional:
* 
Stroke of Fate deals more damage when it hits more targets which makes it very effective in dealing with Lycan and his units.
* 
Soulbind prevents Lycan from running away and makes him very easy to deal with.
Lycan
* 
Faceless Void can lock Lycan down with his 
Chronosphere pinning him down as long as his ultimate is up.
Lycan
* Heroes who summon multiple units that are not spell immune. Nature's Prophet,Lycan,
Beastmaster
Lycan
* Heroes who rely on physical damage output to be effective will fare badly against Muerta's 
Pierce the Veil: 
Phantom Assassin, Terrorblade, 
Drow Ranger, 
Lifestealer, 
Anti-Mage, 
Alchemist, Lycan, 
Clinkz, 
Sniper.
Lycan
* Melee heroes who rely on summons, illusions, or clones will trigger Counter Helix more often, thus taking more damage: 
Meepo, Lycan, Phantom Lancer
Additional:
* 
Berserker's Call can keep Lycan in place during his Shapeshift even through 
Black King Bar.
* 
Counter Helix is very effective against Lycan because of his summons.
* 
Culling Blade will prevent Lycan from running away with Shapeshift when he drops low.
Slardar
* Illusion heroes like the aforementioned Phantom Lancer or Naga Siren, or heroes that tend to buy Manta Style, like Luna or Juggernaut, will give Slardar a hard time, as his damage is single-targeted.
Lycan
* Heroes with summoned units don't fare well against Dawnbreaker. (Phantom Lancer ,Beastmaster ,Lycan).
Lycan
* Heroes who have summons, which can be quickly cleared by his powerful area of effect skill: Nature's Prophet, 
Enigma, Lycan
Lycan
* Heroes that heavily depend on illusions or summons, (Naga Siren, Terrorblade, Phantom Lancer, Lycan,...) are vulnerable to Sleight of Fist and even more so if Ember Spirit has 
Battle Fury.
Slardar
* Slardar does not do well against multiple targets, as his only way to damage multiple targets is Slithereen Crush.
* Meepo's 
Earthbind will root Slardar, making him unable to chase/escape for the time being. Also, 
Poof's low cooldown and high damage can burst Slardar down rather quickly.
Slardar
* Heroes who can stun multiple units at once: 
Dark Willow, Spirit Breaker, Slardar, 
Invoker, and Tidehunter.
Slardar
* Slardar has high priority on building moblity items such as Blink Dagger rather than tank items. Zeus can easily deal large amount of damage to him if not caught out of position first.
Lycan
* Once you get a Black King Bar, squishy spellcasters like 
Zeus, 
Skywrath Mage and others will be probably easy to deal with.
Lycan
* Lycan's Shapeshift can easily to catch from Spirit Breaker's with 
Charge of Darkness.
Additional:
* Vision from Charge of Darkness will easier to catch Lycan Shapeshift and Charge of Darkness out of reach Lycan Summon Wolves and Lycan's other creeps. Until upgrade 
Aghanim's Scepter faster catching Lycan Shapeshift
* 
Howl can dispell with Bulldoze.
Lycan
* Heroes with summons and illusions as Spirit Breaker has no strong AoE capabilities to deal with them: Chaos Knight, Phantom Lancer, Terrorblade, Naga Siren, Broodmother, 
Warlock, Visage, Nature's Prophet, 
Shadow Shaman, Lycan.
Lycan
* Phantom Assassin's 
Blur is a real problem for Lycan, as he relies entirely on direct attacks to deal damage.
Lycan
* Heroes with single-target abilities will be overwhelmed by Lycan and his summons: Wraith King, 
Bane, Phantom Assassin.
Lycan
* Lycan relies heavily on right clicks making Untouchable very effective against him.
* If he tries to run away Impetus will do huge amounts of damage.
Additional:
* She can 
Enchant one of the wolves to her side.
* Lycan will struggle greatly to harm Enchantress through her 
Untouchable which can seriously slow down Lycan's attack speed even if Lycan is spell immune.
Lycan
* Heroes with haste can negate Enchant's slow: 
Weaver, 
Dark Seer, Lycan, 
Centaur Warrunner.
Slardar
* Slardar is one of the few meele heroes who can lane against Ursa in the early game, out harassing him with Bash of the Deep, and running away from a bad engagement with Guardian Sprint
* Corrosize Haze can force Ursa to cast 
Enrage defensively instead of offensively
* With Corrosize Haze, Slardar's team can quickly dispatch of Roshan, denying one of Ursa's greatest advantages
Lycan
* Lycan's ultimate makes him immune to slows from Ursa's 
Earthshock as well as allowing him to outmaneuver Ursa during Enrage. Lycan can also easily chase down Ursa while shapeshifted, should Ursa try to flee.
Slardar
* 
Corrosive Haze hinders Nyx Assassin's ganking attempts with Vendetta, as well as reducing his armor and make him very vulnerable due to his low health pool.
Lycan
* Lycan's high health allows him to easily shrug off Nyx Assassin's burst damage and fend him off.
* As Lycan commonly buys Black King Bar, he can use it to freely attack Nyx Assassin and chase after him with Shapeshift.
Slardar
* Slardar always purchase Blink Dagger can combined Guardian Sprint will catch escaping her with 
Windrun and also avoided from 
Focus Fire after Slardar's sucessful stunned her with Slithereen Crush.
* Corrosive Haze from Slardar is very effective from low armor Windranger's although build Aghanim's Scepter, invisibility from Windrun is useless detected true sight against Corrosive Haze and can easily catch Slardar's kill her.
Additional:
* Low armor from Windranger's so the primary target use Corrosive Haze although her get Aghanim's Scepter, Windrun invisibility so useless and accessible by Slardar.
* Slardar's can easily catch her with combinating use Blink Dagger and 
Guardian Sprint also Slardar's can escaping avoided from Focus Fire.
Lycan
* Windranger's has bad against Hero heavily strong escape out of reach with windrun: Spirit Breaker, Lycan, 
Storm Spirit, 
Earth Spirit
Slardar
* Heroes with spells that negate invisibility such as 
Bounty Hunter, Zeus and Slardar prevent her from saving her allies with Moonlight Shadow.
Lycan
* Mirana's Leap is ineffective if Lycan uses Shapeshift. It also allows him to dodge Sacred Arrow.
Slardar
* Slardar can use Guardian Sprint with Blink Dagger or 
Shadow Blade to get close, and 
Slithereen Crush will stun Sniper and slow him, making him vulnerable to Slardar's teammates.
* Corrosive Haze lowers Sniper's armor and makes Sniper's Shadow Blade useless, easily killing him with a few attacks.
Lycan
* You can easily kill a squishy Sniper, due to your high movement speed and his lack of escape.
Slardar
* Corrosive Haze and 
Bash of the Deep will make short work of Huskar's low armor, even if Slardar is alone.
Lycan
* Heroes with low armor and little mobility, like 
Huskar, 
Io, etc. will also have an unfortunate fate.
Slardar
* Slardar's Slithereen Crush allows him to stun Spectre and illusions, and Corrosive Haze prevents her from juking with 
Spectral Dagger.
Lycan
* The movement speed granted from Shapeshift means that Spectre has no way to punish Lycan if he wants to splitpush or pick off supports. Furthermore, he will kite 
Haunt and cannot be slowed by Spectral Dagger.
* Lycan is often part of an early game push strategy which is often the best counter to Spectre because she needs a lot of time and space to come online as a late game carry.
Slardar
* Heroes who can provide True Sight are always credible threats: Slardar, Bounty Hunter, especially Zeus since his 
Lightning Bolt provides True Sight without the need to detect her beforehand to apply the debuff. So even a late-coming Zeus can easily scout a large area to reveal her, and she cannot purge herself from his sight with the dispel talent.
Lycan
* Multiple attackers thanks to summoned units or clones: Meepo, 
Witch Doctor, Lycan, Enigma, Shadow Shaman
* Heroes that can quickly deal damage to her, regardless of how weak they are, can easily break through her Refraction:
* Multiple attackers thanks to summoned units or clones: Meepo, Witch Doctor, Lycan, Enigma, Shadow Shaman
* Multiple attackers thanks to illusions: Phantom Lancer, Chaos Knight, Naga Siren (bonus for her 
Ensnare). Also despite the visual effects, Templar Assassin does not spill damage against illusions or buildings, so she is not a really good hero to clean up illusions.
* Weak damage but high tick rate or persist in a long time: 
Slark, 
Gyrocopter, 
Queen of Pain, Shadow Shaman (
Shackles), 
Jakiro, Pugna, 
Doom
Slardar
* Heroes with high physical damage can damage Lifestealer more than he can heal: Bristleback, Clinkz, Luna,
Shadow Fiend, Slardar, Terrorblade
Lycan
* Heroes with summons: Lycan, Broodmother, Visage, Nature's Prophet, Warlock.
Lycan
* He can send wolves to defuse 
Proximity Mines, and he can catch up Techies and kill him before they can deny themselves. Even if the suicide is successful, Lycan can still survive because of his tankiness.
Lycan
* Shapeshift allows Lycan to get close and disable Marksmanship.
* Shapeshift also makes him immune to slows like Drow Ranger's Frost Arrows.
Additional:
* The Wolves's speed causes the knockback from 
Gust to be ineffective.
* Drow Ranger lacks escapes and loses her 
Marksmanship when someone is near her. Lycan can take advantage of these weaknesses of Drow Ranger.
Slardar
* Corrosive Haze reveals Pudge's location, making it hard for him to use Meat Hook from the fog of war on Slardar's teammates or Slardar himself.
* Slithereen Crush interrupts Pudge while he is using Dismember.
* Guardian Sprint allows Slardar to avoid Meat Hook.
Additional:
* While Slardar has Guardian Sprint activated, 
Rot cannot slow him and 
Meat Hook is easier to avoid.
* Slithereen Crush allows Slardar to interrupt 
Dismember at close range (when Slardar is not a target).
* Corrosive Haze reveals Pudge's location, making it very difficult for him to land hooks from the fog.
Lycan
* Shapeshift allows Lycan to chase down Earth Spirit.
Slardar
* Shadow Fiend, a normal Shadow Blade builder often relies on its invisibility to escape fights. Corrosive Haze reveals Shadow Fiend and also weakens his already low armor.
Slardar
* 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.
Slardar
* Weaver relies on 
Shukuchi to escape and kite enemy heroes. Slardar's Corrosive Haze lowers armor and reveals Weaver, who is already a very frail target.
* Weaver usually builds 
Linken's Sphere, Corrosive Haze can be used to pop the spell block, additionally the level 25 undispellable talent will prevent Weaver from removing Corrosive Haze with 
Time Lapse, allowing allied heroes to use their abilities on Weaver.
Additional:
* Corrosive Haze lowers armor and reveals Weaver during Shukuchi, who is already a frail target. In addition, Weaver usually builds Linken's Sphere, and Corrosive Haze can be used to "pop" the spell block. His level 25 talent can also make Corrosive Haze undispellable by Time Lapse, which puts Weaver in an even worse situation.
* Guardian Sprint can dodge Weaver's bugs with the movement speed bonus.
Lycan
* Shapeshift is useful for killing or escaping Silencer.
* Summon Wolves, can be used to hunt and harass silencer - even when Lycan himself can't fight.
Slardar
* Corrosive Haze provides True Sight on its target, exposing Bounty Hunter's position regardless of Shadow Walk.
* Guardian Sprint gives a very high movement speed bonus, allowing him to chase Bounty Hunter even if Slardar is tracked.
Additional:
* Bounty Hunter's 
Shadow Walk is rendered useless with Corrosive Haze and makes Bounty Hunter an easy target for Slardar and his team.
Lycan
* Howl reduces a good chunk of Marci's attack damage that she relies heavily on, and the armor reduction works better on her because of her low armor.
* Shapeshift renders Lycan immune to slow from Rebound and Unleash.
Lycan
* Shapeshift allows Lycan to escape from Upheaval with maximum movement speed.
* Warlock doesn't have a good solution to deal with Lycan's wolves from Summon Wolves.
Lycan
* Lycan doesn't care much about Lich's slows thanks to Shapeshift.
* Chain Frost can bounce to the wolves that Lycan summons.
Additional:
* 
Lich possesses a lot of slows, which Lycan doesn't care about when he Shapeshifts.
* Lich has no in-built escape, which makes him a good target for Lycan.
Lycan
* Shapeshift increases Lycan's movement speed and renders him unslowable, allowing him to easily avoid and escape Ancient Apparition's abilities.
* Lycan has fast summons, both his wolves from Summon Wolves can do heavy damage to Ancient Apparition due to his immobility and low armor.
Lycan
* Void's slow is useless against Lycan by activating Shapeshift.
* Night Stalker's single target abilities (with the exception of Void upgraded by Aghanim's Scepter) is not very effective against Lycan's Summon Wolves during the early and mid game.
Slardar
* Corrosive Haze works much like 
Track, giving the enemy team vision over Riki. While it doesn't give a movement speed or gold bonus, it instead can melt Riki's armor and Slardar can use Guardian Sprint to catch up to him.
* Slardar's 
Aghanim's Shard, causes Slithereen Crush to apply Corrosive Haze even if Slardar does not have vision over him.
Additional:
* Corrosive Haze makes Riki completely vulnerable to Slardar and his allies, as Riki has no easy way of dispelling it.
* Slardar's physical damage with Slithereen Crush and Bash of the Deep amplified by Corrosive Haze can easily kill Riki.
Slardar
* Slardar can reveal Clinkz with Corrosive Haze and make him easy to kill, and his Bash of the Deep also hits hard against Clinkz's naturally low health pool.
* Slardar's Guardian Sprint can catch up with Clinkz's Skeleton Walk.
* The stun and slow from Slardar's Slithereen Crush can hold Clinkz in place.
Additional:
* Clinkz survivability depends entirely on 
Skeleton Walk. Corrosive Haze not only makes its invisibility useless, but also makes Clinkz even more vulnerable to physical damage.
Slardar
* Slardar deals entirely physical damage. He does not have to worry about Counterspell.
* Slithereen Crush and Bash of the Deep prevent Anti-Mage from using Blink, the latter even if Anti-Mage activates Black King Bar.
* Corrosive Haze allows allies to take down Anti-Mage before he has a chance to Blink, and maintains vision over him even if he does Blink away.
Additional:
* Slithereen Crush and Bash of the Deep deals physical damage, bypassing the magic resistance bonus from 
Counterspell
* Corrosize Haze significantly increases the damage dealt against Anti-Mage, and makes it harder for him to flee with 
Blink, although Anti-mage can block its casting with with Counterspell
Lycan
* Lycan can clear waves of Chen's creeps with his wolves from Summon Wolves, especially once Lycan takes +2 Wolves summoned talent. And even though Chen can convert one of his wolves with 
Holy Persuasion, Lycan can counter this by buying 
Helm of the Overlord to regain control of it. Uncontrollable wolves summoned from Aghanim's Shard upgrade Summon Wolves cannot be converted with Holy Persuasion.
* Shapeshift allows him to chase down Chen and kill him easily.
* Howl can reduce attack damage of both, Chen and his creeps.
Lycan
* 
Magnetic Field is useless against melee heroes, so Lycan can attack Arc Warden without missing.
* 
Flux doesn't affect Lycan that much, because Shapeshift grants immunity to slows and because he is never alone.
* If their 
Tempest Double has been called, Lycan can still kill Arc Warden before the double expires.
Slardar
* 
Crystal Maiden's already low armor and easily interruptible ultimate, 
Freezing Field can make Slardar her worst nightmare. Crystal Maiden also often builds 
Glimmer Cape which is revealed by Corrosive Haze.
Lycan
* Lycan and Weaver has abilities that allow them to move at maximum movement speed, and those abilities can't be dispelled, potentially wasting the slow from Demonic Purge.
Slardar
* Bounty Hunter and Slardar both have ultimates (Corrosive Haze and Track) that reveal Invoker through Ghost Walk.
Lycan
* Heroes who do not have nor rely on passive abilities make Nethertoxin much less effective: Clinkz, Pugna, Nature's Prophet, Dark Seer, Lycan, 
Tusk
Lycan
* Once you get a Black King Bar, squishy spellcasters like Zeus, Skywrath Mage and others will be probably easy to deal with.
Slardar
* Heroes who can provide True Sight or semi-reveal enemy heroes as Nature's Prophet is prone to buying Shadow Blade: Bounty Hunter, Slardar, 
Spectre, Zeus, Spirit Breaker.
Lycan
* Heroes with single-target abilities will be overwhelmed by Lycan and his summons: Wraith King, Bane, Phantom Assassin.
Slardar
* Slardar can attack through Plague Wards and gain Bash of the Deep charges, and 
Templar Assassin can spill 
Psi Blades through Plague Wards too.
Lycan
* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.
Lycan
* Heroes with single-target abilities will be overwhelmed by Lycan and his summons: Wraith King, Bane, Phantom Assassin.
Slardar
* Heroes with armor reducing abilities greatly hinder Visage's defense like Slardar and 
Dazzle.
Lycan
* Any Hero with high mobility will be neutralized by dream coil: Queen of Pain, Storm Spirit, 
Ember Spirit, Lycan, Bloodseeker, Anti-Mage, 
Timbersaw.
Lycan
* A Lycan with Shapeshift can always run down Puck for a very quick kill due to its low armor. It is important to abuse as many cliffs and trees as possible to escape from a Lycan.
Lycan
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: Lycan, 
Arc Warden, Warlock, 
Chen
Slardar
* With armor items like 
Solar Crest or 
Assault Cuirass combined with Bash of the Deep, Slardar can easily tank the 
Duel, If not dueled himself, he can drop Legion Commander's armor during duel and/or buff his teammate and save them, leaving her only the choice of dueling supports which can also be saved with fast Blink into Slithereen Crush.
Lycan
* Heroes that can summon units will have their summons destroyed very quickly if badly micro-managed, like Chen, Lycan, and Phantom Lancer.
Slardar
* The brutal physical damage of Slithereen Crush and Bash of the Deep can quickly remove Void Spirit's shield and stun him for a while.
* Corrosive Haze provides vision of Void Spirit while he is running away and Guardian Sprint allows Slardar to quickly close the gap
Lycan
* 
Treant Protector grants protection against his attacks with 
Living Armor and his ultimate, 
Overgrowth is a massive AoE disarm and root that pierces spell immunity, causing trouble to Lycan. You will find yourself in need of an ally's dispel or forced to pop Black King Bar for its dispel.
Additional:
* Lycan has no kind of teleport, being only able to walk, and heavily relies on his attacks. As Overgrowth roots and disarms the targets, Lycan can't do much in an overgrowth field.
Slardar
* Corrosive Haze will reveal Treant Protector even when he is under the effects of Nature's Guise.
Slardar
* Terrorblade starts out with and gains a lot of armor from his agility growth. His illusions also make it difficult for Slardar to focus down the real Terrorblade.
Lycan
* Heroes who can summon illusions and summons because Terrorblade has no abilities to deal with multiple enemies at once outside Reflection: Shadow Shaman, Naga Siren, Broodmother, Lycan, Enigma, Chaos Knight, Phantom Lancer, 
Shadow Demon, Dark Seer, Nature's Prophet, Invoker, 
Morphling, Visage, 
Grimstroke with Aghanim's Scepter.
Lycan
* 
Dragon Knight's insanely high armor and splash damage can cause Lycan to struggle taking him down.
Slardar
* Slardar can chase Dragon Knight down with Guardian Sprint and stun him with both Slithereen Crush and his passive Bash of the Deep. He can also use Corrosive Haze to whittle Dragon Knight's armor.
Lycan
* 
Keeper of the Light has a blind, which causes Lycan to miss his attacks.
Lycan
* Heroes with hastes: Dark Seer, Lycan
Lycan
* Lycan cannot escape from a Pounce even if he uses Shapeshift, and has no disabling abilities to stop Slark.
Slardar
* Slardar's level 25 talent makes Corrosive Haze undispellable, thus providing his allies vision of Slark.
Lycan
* 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.
Slardar
* Guardian Sprint allows Slardar to outrun Bristleback, even when slowed by Viscous Nasal Goo.
* Corrosive Haze's armor reduction makes Bristleback much less tanky.
Slardar
* Illusion heroes like the aforementioned
Phantom Lancer or 
Naga Siren, or heroes that tend to buy 
Manta Style, like 
Luna or 
Juggernaut, will give Slardar a hard time, as his damage is single-targeted.
Lycan
* Lycan is a hero focused entirely on single target physical damage and lacks disables or AoE damage. Due to this, he will have difficulties dealing with illusions or Naga Siren's Ensnare.