Vegetto is easily the most powerful fighter of DBZ. He is the fusion between Goku and Vegeta. They used the potarra earrings to fuse, and although this fusion is supposed to be permanent, they separated after buu absorbed them. Vegetto only appears for a brief time in DBZ, when super buu tries to destroy the earth. Vegetto can go super-saiyan easily, and let himself get absorbed by buu in order to free his friends from buu. If Goku and Vegeta do the fusion dance like Gotenks, they'll end up as a fusion called Gogeta.
Attacks: big bang attack, final kamehameha, barrier, ki volley.
Power level at beginning of DBZ: N/A
Power level at end of DBZ: 600,000,000
Class: Fusion