Kai

Kai is an ability specific to the Fighter kit Kensai in Baldur's Gate II, Baldur's Gate: Enhanced Edition, and Baldur's Gate II: Enhanced Edition. Starting at level one with a single use, it may only be used once per day for every four levels.

Effects
Kai allows the Kensai's weapons to do maximum damage for ten seconds after the activation of the ability. The game engine applies this by by setting the warrior's DAMAGELUCK modifier (which accounts for the seemingly random variation in damage that a character can do from one hit to the next) to its maximum value, 20, for ten seconds.

In-game description
"May use 'kai' ability one time per day for every 4 levels (starts at 1st level with one use): this ability lasts 10 seconds and makes all attacks do maximum damage."