Viper/Counters

Bad against...
Viper primarily deals single-target damage and can get quickly overwhelmed by multiple Phantom Lancer illusions. Since Diffusal Blade is core on Phantom Lancer, it rapidly burns Viper's mana leaving him unable to cast Poison Attack or Viper Strike. Also, since Diffusal Blade deals physical damage, it is not reduced by Corrosive Skin.
 * Reason

Illusion heroes generally excel against Viper. When in ultimate form, Chaos Knight's high damage output can quickly kill Viper before he has chance to deal any damage himself.
 * Reason


 * Reason


 * Reason


 * Reason

Others

 * Entry
 * Entry
 * Entry

Items

 * Entry
 * Entry
 * Entry

Good against...
Corrosive Skin's damage reduction is extremely effective against Zeus because he deals magical damage almost exclusively. Zeus uses his spells for last hitting in the lane and takes constant damage from Corrosive Skin.
 * Reason


 * Reason


 * Reason


 * Reason


 * Reason

Others

 * Entry
 * Entry
 * Entry

Works well with...

 * Reason


 * Reason


 * Reason


 * Reason


 * Reason

Others

 * Entry
 * Entry
 * Entry

List of heroes that counter Viper, and list of heroes that work well with Viper.