In DC Comics, Doomsday is the name of the villain responsible for killing Superman. Doomsday is the result of an alien genetic experiment conducted hundreds of thousands of years ago. A nearly indestructible, unstoppable creature, Doomsday was designed to be the top of the evolutionary scale. After he escaped his underground prison, Doomsday headed towards Metropolis, leaving a trail of destruction in his wake.

After an extended battle that left the Justice League of America and Metropolis in ruins, Superman managed to stop Doomsday at the seeming cost of Superman’s own life.

Superman has battled Doomsday twice more. The second meeting left Doomsday stranded at the end of time. The last time, Superman and the new Justice League of America had to stop Doomsday after Brainiac took control of him.

On a side note, many comic book Superman fans were pissed at the thought that a totally new, unheard of villain, which Doomsday was at the time, being able to kill Superman. Most agreed that if Superman should perish, it should be at the hands of one of his old foes, like Lex Luthor.