Parry (Melee 1.0) grants a chance to knock down a melee attacker while Blocking. In Melee 2.0, this mod gives a chance to automatically perform a counterattack against enemies in melee when blocking while Channeling.
As of Update 13, the Parry mod will only work if one is performing Melee Channel while blocking against melee attacks. When successful, a counterattack will be initiated, which momentarily stuns an enemy and allows them to be killed using a melee attack prompt similar to Stealth Attacks.
All melee attacks can trigger a counterattack, including rifle butt strikes by ranged attack units like Lancers and Crewmen.