Piccolo (Dragon Ball)

Piccolo is a fictional character from the manga Dragon Ball by Akira Toriyama. The character also appears in the Anime Dragon Ball, Dragon Ball Z, Dragon Ball GT and Dragon Ball Super. He is the child and embodiment of Piccolo Daimao, who was defeated by Goku. First goal of Piccolo Junior is to defeat Goku in a battle, avenging his father's death. However Piccolo is defeated by his rival in the final match of The martial art tournament, instead of killing him Goku let him live. 
Later in the story he trains Son Gohan,son of Goku, while Goku was dead in order to make him stronger.