Aku is the central antagonist of the cartoon Samurai Jack. He is an evil, shapeshifting demon that has taken over the world and ruled for countless eons. He was voiced by the late Mako Iwamatsu, who also voiced Master Offay from Super Robot Monkey Team Hyperforce Go! and General Iroh from the first and second seasons of Avatar: The Last Airbender. Though he is capable of shifting form into virtually anything he wishes, his standard form is a roughly humanoid being with a black body, a green mouth, and a red beard extending from the bottom of his chin. He also tends to have six horns, four long and two short, extending from his head, and eyebrows made of red, flickering flame. In his standard form, he also tends not to have legs, with his body simply ending at the bottom with robe-like darkness that sometimes manifests as flames, and he also tends to be several stories tall. 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 beaten him on numerous occasions, Aku merely transforms into a creature and escapes, usually calling out a taunt over his shoulder, a fact that he is entirely aware of and even lampshades in "Episode XLVIII: Jack versus Aku". 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. Aku means "Evil" in Japanese. It is written as "悪" in Kanji. The kanji can also be pronounced as "Waru".
