it's naruto. As for guys like hiruzen or itachi, it is an already established fact...but in naruto's case what is really wierd is that most villains start believing in him. He changes a villain's heart just buy saying the same ''i'll never give up, i'll protect every1'' stuff...first zabuza, then gaara and even nagato ! It just spoils their villain character. And defeating kurama by his emotions and making him his partner was just way too much....i mean kurama is the strongest of the bijuu. No doubt plot requires naruto to play his role this way but changing every character's heart is absurd. And recently kishi did make him kinda invincible with insane inhuman powers. Even the most powerful ninjas like itachi or hiruzen have their limitations or weaknesses but naruto seems to have no weakness anywhere!!! however what i say doesn't actually matter because it's kishi's manga after all.....