Uub

From Dragon Ball - Wiki on Neoseeker

Uub

A young human boy who was born as the pure-hearted resurrection of Majin Buu. At the very end of Dragonball Z, Uub met Goku in a martial arts tournament and was trained by the Saiyan over the next ten years to learn how to use his inner power. He later merged with Good Buu in Dragonball GT, becoming much stronger and fought Baby afterwards, but came up short.