Viper/Counters

Bad against...
Viper primarily deals single-target damage and can get quickly overwhelmed by multiple Phantom Lancer illusions. High mobility of the Phantom Lancer will allow him engage and disengage indefinitely while slowing Viper with, making Viper absolutely helpless. Phantom Lancer also benefits a lot from purchasing, and it's one of the best items against Viper.

Illusion heroes generally excel against Viper. After casting, Chaos Knight's high damage output can quickly kill Viper before he has a chance to deal any damage himself. Also, Viper has almost no way to deal with the illusions.

The pure damage provided by is a great counter to Viper, as it is not reduced by. Additionally, prevents the slow and damage over time from both  and. Also, can negate Viper's physical damage output.

Viper can be ganked early via ​, his game tempo can be slowed as is a great outpushing skill. Viper primarely deals single-target physical damage, so well-timed ​ on the targed focused by Viper can be gamechanging. Succesful ​ can make Viper kill one of his teammates, or lock Viper down.

Viper is an agility hero, and his itembuild mostly include agility items, so ​ can be devastating, removing all armor and vastly decreasing the effectiveness of, weakening Viper's magic resistance. Additionaly, and ​ deal both magical and physical damage, and can help bringing Viper down fast.

While being highly mobile hero, Windranger doesn't need to be afraid of getting slowed by, as she can dodge it with ​. Additionaly,  can be easily landed on Viper as he is slow and have no abilities to disjoint it. grants Windranger vast amount of single target damage output, so she can cut through Viper's natural tankiness. And finaly ​ is a great laning tool against Viper, as it helps Windranger staying away from ​ harass most of the time.
 * Windranger's skills can be somewhat countered by Viper purchasing and  or  or.

Tinker can matchup fairly well with Viper on the lane as deals pure damage and prevents Viper from harassing with. High mobility later on with and  will allow Tinker staying away from the fight with Viper while constantly harassing him with  and, limiting Viper's pushing capabilities. Late game with  can lock Viper down indefinitely, leaving him helpless.

Possessing two strong disables - and  as well as high physical damage with  Shadow Shaman can become a big problem for Viper.

Laning against Broodmother will be an absolute disaster for Viper, as early levels of can't protect him against Broodmother's spiderlings. Later on Viper has no way of stoping Broodmother's push as he has no AOE damage. Additionaly, Broodmother can bring Viper down fast with on.

Enchantress can pressure Viper with tamed Neutral creeps. Her can help saving teammates while  will allow her to be safe herself. Later on is devastating against Viper as pure damage isn't decreased with, while  won't allow him to escape

Others
Invoker is really weak against Viper in the laning stage, and can be harassed hard out of the lane, but when surviving through it can become a problem for him. Invoker possesses big arsenal of skills that can make Viper's life ugly, including strong kiting spells (, and ), mana burn, high damage dealing skills , disables , and strong summons  that can melt Viper's armor. Through all this Invoker is still weak if pinned down with and.
 * is highly reccomended against Invoker.

Generally Viper is very good against Ursa, as he can kite him with. But when initiating onto Viper via Usra can burst him down in a few seconds, before he will even be able to turn for ulti. Viper won't be able to escape once is applied. Ursa can also tank Viper attacks for long time with.

Items

 * - Viper has no natural way of stoping channeling spells, so enemy hero can escape even when slowed hard by and.
 * - Viper can easily get jumped on with a and disabled. As Viper is not very fast,  can also be somewhat reliable way of escaping,. Disjoints.
 * and - somewhat effective items for saving from Viper's regular attacks.
 * can help saving teammate or yourself from Viper. Magic ressistance halps against and.
 * can be crucial tool for saving teammate or yourself from and  slow.
 * - Break can disable both and  making Viper a lot less tanky and reducing his damage output.
 * - reliable way of disjointing.
 * - if possessed by any enemy hero will significantly decrese Viper's damage output.
 * - Viper has no way of escaping a hero with a as he has no natural escape skills. Aslo  works great against Viper, as it's damage type is physical.
 * - when focused with Necronomicon units Viper will get his mana burned, making him unable of using and.
 * , and  will allow enemy heroes become more tanky against Viper because of miss chance and high armor boost from agility bonus . Also 's active ability will disarm Viper.
 * , and  are all tank items that will allow enemies survive Viper attacks or manfight him. Additionaly, 's lifesteal counters Viper's  and  allows chasing Viper while slowing him hard.
 * and - can both lock Viper down.

Good against...
Zeus is extremely fragile and can easily get bullied out of the lane with harass. '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. Viper is also potent, and  carrier.

Viper provides excellent damage over time to burn through charges with,  and.

Queen of Pain suffers greatly from harass. when casted on Viper will cause deal comparable amount of damage back to Queen of Pain, so she can't harass Viper at all. is also not really dangerous for Viper because of.

Sven can easily get bullied out of the lane with harass. He's generally really weak agains kiting and his damage is rarely enough to bring Viper down upon initiation, so is extremely effective, as the slow is not disbled even by.

Tiny can easily get bullied out of the lane with harass. is extremely effective against Tiny skills, providing magic ressistance. provides heavy slow upon Tiny lategame, when his regular attacks are potent. Viper can also deal heavy damage while not being endangered by.

Dragon Knight can easily get bullied out of the lane with harass, while Viper is tanky enough with  for not to be endangered by. Even when affected by Dragon Knight is a lot weaker than Viper and can't manfight him.

The same reasoning with works with with most melee heroes like:

and so on...

Others
Huskar suffers from harass, but being ranged can contest the lane. is great agains Huskar as he prefers fighting being on low HP. Midgame to lategame this matchup can go both ways, depending on plays, map movements, farm speed and so on. Machup favors Viper, but Husar can bounce back.

Works well with...
greatly increase Viper's attack damage, making his laning phase even stronger. Also, enemy caught by has no way escaping with all the slow from,   and.

Viper provides great damage inside the Void's.

can help Viper catch up with enemy, while and  amplifies Viper's damage.

Slardar provides Viper with lockdown from and even more single target damage with.

Io increase Viper's tankiness even more with and, as well as attack and move speed. makes up for Viper's lack of mobility.

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