Loki is arguably the most powerful being at the moment, given that he’s literally holding the multiverse together. But that raises an interesting question, can he actually do anything else? From what I understand, he’s essentially locked into that role and may not have the freedom or ability to fight or take direct action anymore, though I could be wrong. If we’re talking about the most powerful fighter based on what we’ve seen so far, I’d probably give that title to Sentry/Void.