Warning: Major Spoilers ahead for Batman V Superman: Dawn of Justice.
This weekend finally saw the release of Batman V Superman: Dawn of Justice, which overcame negative reviews to earn over $400 million globally, making it the biggest weekend ever for a comic book adaptaiton.
It did so, in part, by leaving a lot on the table. Batman V Superman took elements of the best-selling Superman story in decades, and the best-selling Batman story in decades, and blended them into a tale that establishes the DC Extended Universe and sets up a showdown between the Justice League and Darkseid's Apokoliptian hordes.
Along the way, fans were introduced to Doomsday.
In the comics, Doomsday was a rampaging beast of indeterminate origin, but was eventually revealed to have been a genetically-engineered weapon of mass destruction, whose first sentient act was to kill its creator on ancient Krypton before beginning an existence that saw it moved from world to world over the course of centuries.
In Superman: Doomsday, an animated feature film from a few years back, Lex Luthor was involved with releasing Doomsday on the world, and he was tied to the beast in All-Star Superman as well, so replacing ancient Kryptonian scientists with Lex isn't without precedent, but it's not the creature's comic book origin.
In the comics, Doomsday battled with Superman from rural Ohio all the way east to Metropolis, where he and the Man of Steel finally collided in one massive, final blow that left both of them dead.
After that, Doomsday was taken to a laboratory where they studied him until his body was stolen and thrown into space (more on that soon), and Superman's body was interred at a tomb in Metropolis following a massive state funeral. Newly-elected President Bill Clinton spoke at the service, and there was a massive cortege made up of supporters, heads of state, other superheroes, and more. Members of the Justice League served as Superman's pall bearers, while his parents buried a small box full of his favorite childhood things in a corn field where his rocket had once landed.
After Superman's body was stolen (twice), and finally returned, it disappeared once again...just after Jonathan Kent had a near-death experience in the hospital and believed himself to have lured his son back from the edge.
It later turned out that Superman's body had been stolen at first by Cadmus Labs, who managed to make a clone using genetic material from both Superman and Cadmus Director Paul Westfield; the second time, it was The Eradicator, a Kryptonian AI and former supervillain who put Superman's body into a regeneration matrix (like a giant, fluid-filled egg that bombarded him with solar energy).
Both the Cadmus clone (which was rapidly aged to 16) and The Eradicator took to the streets to stand in for Superman in his absence, each of them claiming to be Superman. Another man -- a cyborg who appeared to be Superman with the same damage he suffered from the Doomsday fight -- also appeared claiming to be Superman. A fourth -- a man in a suit of armor with sophisticated weaponry -- appeared wearing the Superman emblem, as well.
Ultimately, none of these four became a "new Superman." the original would eventually awaken and, with The Eradicator, the armored Superman known as Steel, and the teenage clone at his side, take on the Cyborg, who was in fact evil and looking to harm Superman's reputation in the universe by destroying Earth in his name.
Eventually, Superman's body healed to the point where his powers were restored...and the Cyborg Superman was destroyed, although he transferred his consciousness to a beacon he had planted on the corpse of Doomsday when he had previously lashed the body to an asteroid and threw it into deep space for "safety."