Piccolo

Piccolo is the Namekian reincarnation and final son of the original King Piccolo as well as the final villain in the first Dragon Ball series, and a protagonist in the Dragon Ball Z and the Dragon Ball GT series. He was born to avenge his father's death at the hands of Goku. After his narrow defeat against Goku, Piccolo is soon forced to form an, at first, uneasy alliance with him and his friends against newer, more dangerous threats. Thus, he and Goku kick off the formation of the Z Fighters. Also, out of necessity he also takes it upon himself to train Goku's young son Gohan, forming a powerful bond which ultimately redeems him when he sacrifices himself to save the child's life from Nappa. After his resurrection, he fully joins Goku and the others in their struggles against ever more powerful villains. As the story progresses, his role shifts from warrior to mentor. He is one of the most intelligent characters in the series, retaining King Piccolo's tactical genius, and later gaining Kami's great wisdom after fusing with the him.