Uranos is one of the original Eternals, and Thanos's grandfather. He is most commonly known in the Judgment Day storyline, where the Avengers, X-Men, and Eternals are at war with each other and are judged by the progenitor celestial. In this story, Druig, who is the Prime Eternal, sends Uranos to the mutant population on Mars, now called Arakko, and kills 98% of the population. And the thing about it is, all of the mutants that he killed, were Omega level mutants, and he killed them all in 1 hour. That's how powerful he is.