Piccolo
When Goku was a little boy, he faught in the
Tenkaichi Bodukia against Piccolo Daimoah and defeated him with a head butt, and while Piccolo Daimoah was dieing, he spit up an egg of some sort that would soon hatch and become Goku's enemy. The enemy's name was Piccolo also. Later in Dragon Ball Z, Piccolo grew to like Gohan and trained him for the Nappa and Vegeta Saga. And he turned to the side of good, to help Goku, Gohan, and Krillin to battle. Piccolo becomes the strongest being in the universe at one point when he fuses with the namek, Kame, the guardian of Earth. In the Namek/Freiza Saga, he fuses with another Namekian named Nail to make him stronger so he can try in defeating Freiza, but that doesnt happen. He gets brutally beaten. But he is still one of my favorites.