- Main article: Majin Boo
|“||Me Boo! Kill you!||„|
|~ Pure Majin Boo|
Pure Majin Boo or Kid Buu (Funimation dub) is the original form of Majin Boo created by the wizard Bibidi and is also the final villain in Dragon Ball Z. He is also the true main villain of the Buu Saga. He transformed from Evil Majin Boo when Vegeta tore down Majin Buu from his head. The original Majin Boo had his appearance before absorbing South Kaioshin and Dai Kaioshin, and he is a mindless killing machine. With the purity and rationality of the Kaioshins' influence inside of him gone, he is more dangerous as he is a pure, unrestrained evil.
The AnimeAfter becoming Pure Majin Boo, his first act was to blow up the Earth with a giant pink energy ball after Vegeta tells him if he wants to destroy Earth, he has to fight them first, killing Gohan, Goten, Trunks, Piccolo, Tenshinhan, Chaozu, Karin, Yajirobe, and (though it is also possible that Super Buu killed him with his Human Extinction Attack first, depending on whether or not he evaded it) Artificial Human 17. He then used Shunkan Ido to destroy planets until he arrived at Dai Kaio's planet. He fought Kuririn and Yamcha, who were already dead, and nearly blew up the planet before Full power Super Saiyans Goku and Vegeta powered up to draw him over to Kaioshin's planet.
Through rock-paper-scissors, they decided Goku should fight him. Goku first fought Pure Boo in his Super Saiyan 2 state and later, as a Super Saiyan 3, evenly matching with Pure Boo, but began losing his energy due to not having mastered the Super Saiyan 3 state and his earlier battles against Boo, Vegeta fought Pure Boo as a distraction, even though he knew that if he died while already dead, he would not exist anymore and could never be revived again. Vegeta was at a disadvantage and Boo was about to end his existence when Mr. Satan, believing himself to be in a dream, appeared and insulted Boo. Boo tried to attack him, but was unable to because he was getting a headache caused by the original Majin Boo, whom Pure Boo spit out like a piece of chewing gum.
Majin Boo then fought Pure Boo, but Pure Boo had all of the advantage and beat up Majin Boo, with Mr. Satan attacking him (and not doing any damage). When Goku lost all his Super Saiyan 3 energy, Vegeta devised a plan that involved using the Dragon Balls to revive Earth and all its inhabitants (Vegeta and Rou Dai Kaioshin returned as well). Goku then began gathering energy for a Chou Genki Dama, but no one on Earth (aside from other Z Warriors and their friends and families) would give up energy. When Majin Boo was clearly losing energy and close to death, Vegeta re-entered the battle, and Goku asked people to give up energy. A few of them did, but everyone else thought he was trying to steal their souls - until Mr. Satan asked them to, and they did, believing that Satan was the one fighting Buu.Pure Boo caught the Chou Genki Dama as Goku threw it at him and sent it back at him. When Vegeta had Dende use Porunga's third wish to restore Goku's energy, Goku was able to send the Genki Dama back at Pure Boo and destroy him once and for all. Before destroying him, Goku said he would like for Pure Boo to return as a better person, as he was his most worthy opponent yet. Lord Enma heard this and, after Pure Boo's death, reincarnated his body into a human child named Uub, who unlike his previous self, was not evil. After he fought Goku in the World Martial Arts Tournament, Uub becomes Goku's student and Goku decides to live in Uub's Village as his mentor so he can train him.
- Kid Buu is the only one of the four main villains Goku actually killed.
- Vegeta's life was spared by Goku.
- Frieza was beaten half to death by Goku, but survived their battle and was rebuild as a cyborg, and then was killed by Future Trunks.
- However in the 2015 movie, Resurrection 'F', a newly revived Frieza is killed by Goku.
- Cell was killed by Goku's son Gohan, but Goku did help Gohan defeat Cell.
- Kid Buu is the only main villain who doesn't have a tail.