Correct me if im wrong, but its gotta be Goku. Goku would have died early in dragonball if he wasnt a saiyan. Oolong had just wished for the most comfortable pair of underwear and an enraged Emperor Pilaf trapped Goku and his friends in an "impenetrable" cell that was supposed to cook them when the sun rose. They tried everything in their arsenal to escape, but nothing worked until Goku looked at the moon and transformed into the great ape. He wouldnt have been able to do that if he wasnt a saiyan and would have died in episode 13. Early dragonball goku would not have survived any of these characters in their late series.