Well, that's one cartoon character I'm going to be looking at differently from now on.
OT: I really do think Satan gets mopped here. I understand that he's only a joke within the context of his series and that he actually does have some decent showings, but Leonardo should outclass in terms of skill and has definitely held his own against people far more threatening in his time.
And before "no weapons" comes up, Leo doesn't need them. He's gone through far more than weapons training and is fully capable of fighting with his bare hands.