Impact, also known as Damage is one of 4 weapon workshop upgrades. It is the power of a projectile that takes away enemy's health and armor.
Weapons with highest damage are Explosives, while Elementals have the worst impact, which makes them one of the weakest weapons types. High damage is often balanced by low fire rate, although some weapons have both stats high, which results in them being overpowered. Iron Curtain is the best example of that.
Impact is sometimes reduced when a weapon is custom, for balance.But it can be upgraded to get back to normal. Damage decrease is a common negative side effect of most Attachments that give the weapon significant power instead.
Most of Offensive Upgrades for hero increase weapon impact. Laser Sight increases damage done with criticals by 15%. Ballistic CPU increases headshot damage by 10%. Heavy Load increases damage on long ranges by 5%. Sharpened Edge increases melee damage by 10% (damage done with Blades).