Aku

"Long ago in a distant land, I, Aku, the shape shifting master of darkness, unleashed an unspeakable evil. But a foolish brotherhood stepped forth to oppose me. Before the final blow was struck, I used a curse on them all, and killed them. now in the future where my evil is law. A group of heros seek to undo my evil and the future that is Aku."

- Aku Aku is the main antagonist of the cartoon Samurai Jack. He is an evil, shapeshifting demon that has taken over the world and ruled for countless eons. Throughout the series, he was voiced by the late Mako Iwamatsu in the original series but was replaced by Greg Baldwin in Samurai Jack Season 5 despite of Mako's death in 2008.

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".

History
in 1992 Aku attacked the earth and killed the brotherhood of kells, thus creating Earth 17, where he now rules the earth. In 2017 Samurai Jack meant a group of 2 Pikmin and a reincarnated Kirby, who meant Splash and tried to reform the brotherhood.

Battle of Shengai
One of Aku's minions, Shinobi, inslaved those who tried to rise up against Aku and his army. While trying to make a peace treating with Shinobe, king of the slimes and former brotherhood member, a prision break lead by the new brotherhood happend.

Season 3
Aku is one of the main antagonists in season 3. He first tries to kill the brotherhood by using inquisitors and bounty hunters, until he made a deal with his cult in "Flashback".

The High Priesstess
"I can't stand these god damn cultist anymore! You just sit there and speak to a statue of myself, meanwhile I try to kill them!......Don't fail me with these assains, or else."

- Aku Aku seems to be annoyed with with his cult.