Quickly. Morgoth was already defeated and there was no reason for a duel. Some accounts give that Ëonwë was a superior fighter to Morgoth, regardless.

I don't really want to answer the question, since I'm more curious as to why you even need to know? I mean if I said he was squished into a little ball and Uinen kicked him into the void would you have any evidence to dispute it?

Still confused.