Moxie

Moxie increases the user's Attack one stage upon fainting an opponent. Stats can be raised to a maximum of +6 stages each.

Game descriptions

Black, White, Black 2, White 2:Boosts Attack after knocking out any Pokémon.
X, Y, O.Ruby, A.Sapphire:Boosts the Attack stat after knocking out any Pokémon.
Sun, Moon, Ultra Sun, Ultra Moon:The Pokémon shows moxie, and that boosts the Attack stat after knocking out any Pokémon.
Sword, Shield, B.Diamond, S.Pearl:The Pokémon shows moxie, and that boosts the Attack stat after knocking out any Pokémon.
Scarlet, Violet:When the Pokémon knocks out a target, it shows moxie, which boosts its Attack stat.