Doomsday

Born without a name, Doomsday was a biological weapon developed to explore the ultimate end potential of Celestial genetic code.

The Doomsday creature was engineered on a world formerly part of the Kryptonian Hegemony. During the years when the Kryptonians were being forced back to their homeworld, an alien scientist working at the behest of the Guardians of the Universe tried to design a beast that could be a physical match to Kryptonians.

The prototypes possessed genetic memory and evolutionary adaptation. Every time it was killed, it was brought back to life with a knowledge of how it died. Over time, forced evolution became natural, and the regeneration autonomous from the control of the scientists. It learned to absorb energy the same way that Kryptonians naturally did. Hundreds of Kryptonian prisoners were supercharged under synthetic sunlight and forced to fight the creature.

In short order the monster grew beyond all control. It destroyed the labs and slaughtered every living sentient on the planet. Hundreds of Green Lanterns were dispatched to contain it; they all died as well. In desperation, seismic pulse-bombs were detonated near the core, rupturing the planet and destroying it utterly.

The creature somehow survived and was flung into deep space. Periodically it would be caught in a gravity well or picked up by a passing ship looking for salvage. At one point he tool control of a spacecraft and made a line directly for Oa, slaughtering legions of Green Lanterns as he did. Doomsday would crash into a world once every few millennia and slaughter until he was defeated or there was no one left. The collective consciousness of an entire planet was gathered to defeat him on Calaton, and there Doomsday seemed to die before being punted into deep space.

Thrown into a dimensional voice, Doomsday was eventually pulled into the stellar regions around the Demiurge. The casket containing his body crashed to ground and the monster emerged, invigorated. A hundred and fifty metahumans attempted to stop Doomsday over the course of the day-long rampage. A few were successful in temporarily halting him, but he would regenerate and return with fresh rage and a new tolerance for their means. Finally, Superman joined the fray and went toe-to-toe with Doomsday. The end result was the defeated monster being hurled into the cosmic void again, and many dead heroes to be mourned-- Superman among them.