Viper the netherdrake is brutal when it comes to one-on-one action. His Corrosive Skin makes him relatively tanky for his low health, and his spammable Q just eats away at your life until there’s little fight left in you.
Hero counters: physical damage is what you need to put Vipe down. Chaos Knight, Phantom Assassin, Lycan, Meepo, and Naga Siren are strong carries to counter with. For utility heroes, think about Keeper of the Light, Elder Titan, and Enigma.
Item counters: Black King Bar can get you up close and personal with Viper, rendering his Q useless for its duration. Blink Dagger will help you close the gap or escape if Vipe gets the jump on you. Lifesteal items (Helm of the Dominator to Satanic) can help melee stand up to Vipe’s DoT.
Next: 29. Lifestealer