Son Goku

He is not a hero. Toriyama said so himself. Goku is a martial artist who happens to keep saving the world, and those are not the same thing. He spared Frieza, who came back and murdered him. He spared Vegeta, who had just killed his friends. He hands enemies senzu beans so the fight stays interesting. Every time it costs someone else. Then in Super he asked Zeno, a child god who erases things without thinking, for a tournament. Eight universes were put on the line because Goku wanted stronger opponents. He is generous, kind, completely without malice, and the most dangerous person in the series for exactly that reason.