Nice points indeed. I will state several things towards them however. Dante needed Vergil's help to defeat Arkham, he couldn't do it on his own. Dante also needed Trish's help to seal Mundus, he couldn't do that on his own either. He doesn't technically kill Griffon, just fatally wounds him. Mundus destroys Griffon for his failure in battle against Dante. Vergil's corruption wasn't in his favour. When he saw the amulet the first time they fought he freaked out. I think his corruption let him down in his battle against Dante, so he definitely wasn't in his own perfect state of mind (Making him weaker). All your other points I've got nothing against, they're good solid points that I respect.