Leviamon may be a pretty large Digimon, but he really doesn’t stand a chance against Diaboromon. Diaboromon’s energy blasts are very large and he can also be pretty quick considering his size. Diaboromon is not the strongest Mega level Digimon anymore, but there was a time where he held that spot very fiercely. I wouldn’t say that anyone ever considered Leviamon to be at the top of the food chain. His water abilities just won’t be enough to win. Diaboromon wins.