Gold Buu is a form of Kid Buu when he absorbs all of the energy of every ki attack that hit him, including the Spirit Bomb. This turned him almost completly gold. After this the knowledge and strength of every being that contributed to the Spirit Bomb, was now in him.
He quickly dominated over Goku and Vegeta. Remebering about Gohan and Gotenks he went back to Earth. Trunks and Goten fused into Gotenks and went Super Saiyan 3. Gohan and Gotenks charged Gold Buu. Gotenks was shot down with a single blast, and Gohan put up a long fight but in the end he fell when Buu threatened to kill him mom. Gohan could only stand there and get killed. After that Buu destroyed the Earth.
He went on a killing spree thoughout the Universe, never to be chalenged by an opponent he could not easily defeat.
He has all the normal abilties of Kid Buu but he also has a few new ones.
- Instead of being like Gum when he is hit, he is stronger then Diamonds.
- He is now a lot smarter then Kid Buu, but does not absorb anyone even though he knows he can because he is so powerful he chooses not too.