Aku is the main antagonist in the cartoon Samurai Jack. He is also known as the "Master of Masters", "The Deliverer of Darkness", and the "Shogun of Sorrow". He was voiced by the late Makoto Iwamatsu.
Aku constantly antagonizes Jack, often attacking him when he is weak, and other times defending himself from Jack's own gambits. The two seem doomed never to defeat each other, for though Jack has bested him on numerous occasions, Aku merely transforms into a creature and escapes, usually calling out a taunt over his shoulder and escapes, a fact that he is entirely aware of and even makes a reference to in episode XLVIII.
While he's usually presented as a serious and threatening foe, Aku is also a source of comedy in the show, due to his outrageous design and sometimes wise-guy behavior, supported by Mako's over the top voice-acting. It means "evil" in Japanese
