Doomsday is a fictional supervillain appearing in comic books published by DC Comics. He was infamous for seemingly killing Superman. The character was an experiment created with the remains of a Kryptonian caveman, when the planet exploded that body was sent flying in a capsule into the Earth's atmosphere with the yellow sun giving it powers as it gave to superman, but the changes they changed the effect of the sun a little on him, with him only having increased physical abilities with him not having the power to fly or to shoot energy through the eyes, and he became able to survive only with the energy absorbed from the sun. When the capsule fell he was wearing a huge space suit that was being destroyed during the fight until only the part that covers the genitals is left. One famous thing is that the character had apparently been killed by the superman who killed himself with effort and injury by defeating him, but just as Superman was brought back with an excuse, Doomsday was established as having the power to always return. In one experiment he started to have a real mind instead of just attacking irrationally as before (experiment by lex luthor).
The original version of his origin was used in the animated film The Death of Superman. In Justice League, it was an experiment done with the one done with Superman's DNA (it was explained that he appeared falling on Earth because he was in a prison in the Earth's atmosphere). In Superman / Batman: Doomsday, he was part of a super-soldier project and there were more than one, he was an army. In Batman vs superman, he was a creature made by mixing Lex Luthor's DNA with General Zod's dead body, as absurd as that sounds. In the Justice League Heroes video game, a Doomsday clone came up with the rule that it can't be beaten twice in the same way. Appears in Lego DC Super-Villains