How to counter Viper in Dota 2

Intensifies Viper's venom, adding an effect to his normal attack that applies a stacking movement speed slow and magic resistance deduction while dealing damage over time. Stacks up to 6 times.

Viper releases a Nethertoxin at the targeted area. Units in that area take an increasing damage over time based on how long they remain in it. Units in it have their attack speed slowed.

Viper exudes an infectious toxin that damages and slows the attack speed of any enemy that damages it in a 1200 radius. The acid exudate also increases Viper's resistance to magic.

Viper slams into the ground, releasing a Nethertoxin and splattering each enemy in a 500 AoE for 4 seconds with the effect of Corrosive Skin.

Viper slows the targeted enemy unit's movement and attack speed while also disabling their passives and dealing poison damage over time. The slowing effect reduces over the duration of the poison.