In Kingdom Hearts, Berserk is a support ability that boosts a character's attack power when their HP is critically low. The ability is especially effective when used together with weapon skills. It costs 1 AP to equip.
In Kingdom Hearts Chain of Memories, Berserk is an enemy card effect that boosts the power of attack cards when HP is critically low. While Berserk is in effect, the player is resistant to fire and is stunned by ice. It costs 40 CP to equip and lasts for 30 attacks.
Kingdom Hearts Final Mix
Kingdom Hearts Chain of Memories
Kingdom Hearts Birth by Sleep
Berserk is a recurring status in the Final Fantasy series that increases the attack power and speed of the affected character, but makes them uncontrollable by the player and forces them to use only physical attacks.