Kang The Conqueror
Species: Human
Enemies: Iron Man, Fantastic Four, The Avengers
Kang the Conqueror is one of the most notable villains in Marvel Comics today. Technically, Kang is born in the 31st Century on Other Earth. Due to being 1,000 years into the future from our present day, Kang has access to A LOT of impressive future technology. Of course, Kang is also a smart man in his own right. This allows him to figure out time travel, which gives him the chance to go back to the past and conqueror several worlds and universes using his future tech and knowledge.
Due to the multiple universes, Kang is able to help versions of himself in those universes do the same as himself. Thus, versions of Kang are split across the multiverse. Whenever there is a need for assistance, Kang copies can show up to assist the vulnerable Kang. That makes him one of the most powerful galactic characters in comics. He’s nearly impossible to stop, putting him in the crosshairs of several heroes. Including notably the Fantastic Four, Iron Man, and The Avengers.