Board Thread:Questions and Answers/@comment-27389023-20160901160206/@comment-24670104-20160901225652

Thanos is said to be the most powerful being in the universe, but as you say, we haven't seen him done anything yet.

I'd say Loki is because he has done a lot of stuff and has commanded an army to invade Earth. Also, he is the most politically powerful person in the MCU that we know of as he is ruling over Asgard and by default the rest of the realms.