Malekith was quite underwhelming as a villain - particularly in comparison to his comic book counterpart - he lacked esoteric powers and relied on the Aether to truly be a massive threat - but the fact is that he was able to go toe-to-toe with Thor in physical combat and that makes him a powerful individual by default. Although he demonstrated fire blasts whilst holding the Aether, he is placed so highly on this list based solely on his baseline power - and that means he's here based solely on strength and durability. He was able to hit Thor with enough force for the Asgardian warrior to feel it and could take shots from him without instantly turning to mist. That means he's a very tough and powerful villain.
