The fish that escaped from Dark Rift has been one of the most dreaded pubstompers in the game. His popularity in competitive matches has also been rising lately.
Slark has good solo kill potential, the ability to be a constant threat around the map and great survivability. He can deal with most Heroes pretty effectively and he can be quite hard to bring down. Slark works best when given just a little bit of space, and in pubs where team coordination is a bit lacking, that bit of space will go a long way.
Still, every Hero in the game can be dealt with, given some prepartion.
Well except Invoker maybe
What we need against a Hero like Slark is a lot of burst damage, preferably AoE. Because of Shadow Dance, right clicks and single target spells aren’t as effective. Vision providers can also hinder his gameplay a lot.
: Our beloved tree hater has tons of AoE pure damage with very low cooldowns, good armor, and he’s hard to chase. A perfect match for Slark who counts on getting pickoffs a lot.
: While Torrent+Boat stuns can be disabled, Kunkka is still a Hero with tons of AoE damage, plus Ghost Ship’s buff will allow his teammates to survive the duration of Shadow Dance. X is still a good spell to initiate, even against Slark.
: Well, this guy is good against pretty much any lineup anyway. He can stun a Shadow Dancing Slark for over half the duration. A well placed Silence on an unsuspecting fish can mean his end.
: Axe possesses one of the few reliable disables against Slark. Berserker’s Call can’t be dispelled and lasts 3.2 seconds, enough to waste most of Shadow Dance. Plus, he’s great against melee Heroes anyway.
: Did you call for AoE? Maybe Earth Spirit is more reliable than the King nowadays, but he still can dish out a lot more damage if that’s what you need.
: Always great for those elusive targets.
: This guy was THE counter back in the day, before he got hit by the nerfstick. If Slark’s HP is low enough, Bloodseeker will give vision of him and negate Shadow Dance’s passive effect. Also, fast Heroes don’t fare well against Rupture.
: While his stun is near impossible to hit on Slark, he still has tons of AoE damage that can pierce through the fish’s defenses.
: A well placed Ice Blast will take away Slark’s huge HP regeneration for a good amount of time.
: Also great amounts of nuke damage, paired with the ability to give vision and true sight.
Special Mention: Illusion carries
  : These are the types Slark is less effective against. His Essence Shift really falls off against them, as it won’t reduce their damage output/HP as much.