Good Buu (魔人ブウ), also known mainly as Majin Buu, is the result of Innocent Buu using fission to split into good and evil halves. He would go on to become a member of the Z Fighters and live with Mr. Satan. After the battle against the pure Majin Buu, Buu is referred to as Buu instead of Majin Buu and to the world he becomes Mr. Buu.
Good Buu possesses the Grand Supreme Kai as part of his being and eventually temporarily awakened this part of himself.