Korvac
Coming from the 31st century, Korvac was a skilled computer technician who betrayed Earth when attacked – the conquerors used his skills in order to supervise entire planets. Being just a regular human, he succumbed to exhaustion and collapsed. His upper body was then grafted to a hovering module, thus making him into an actual cyborg. In this way, he became an even more efficient slave.
In his plans to overthrow his capturers, he became entangled with the Grandmaster, one of the most powerful supervillains in the universe. Using his skills, he managed to copy Grandmaster’s knowledge and powers. After encountering a mighty team led by Thor and the Guardians of the Galaxy, he flees into the 20th century. In here, he finds the ship of Galactus and steals all the knowledge it stored.
In this way, he becomes almost omnipotent, able to defeat all the Avengers and Guardians of the Galaxy all alone. His ultimate purpose was to rid the universe of all the chaos. In his final fight, he wasn’t killed – he simply committed suicide and allowed the remaining Avengers (Thor, Vision, and Iron Man) to deliver the finishing blow, not before reviving the superheroes who were already killed.
So Korvac is one of the supervillains who can defeat all most well-known superheroes. His abilities come from his contact with future alien technologies, from syphoning the knowledge and powers of the Elders of the Universe, and from copying the powers of Galactus himself. He is one of the supervillains who literally has infinite power.
