In Superman: Doomsday, an animated feature based closely on on the epic DC Comics story "The Death of Superman", Superman (voiced by Adam Baldwin) battles against the seemingly indestructible creature known as Doomsday. The battle between the two super-powered titans drags out for several minutes with Superman at the apparent disadvantage since Doomsday is unhindered by emotion, feels no pain and appears to be physically stronger. Refusing to let Doomsday destroy Metropolis, Superman - though weakened after being ferociously beaten - grabs Doomsday and flies far up into the sky, achieving orbit. He then plummets down to Earth again with he and Doomsday still pounding each other as they re-enter the atmosphere. The two adversaries come crashing down like a comet in Metropolis, and when the dust settles, Doomsday is dead and Superman appears to die seconds later, collapsing in front of his love Lois Lane.
Following Superman's apparent death, his body is buried in Metropolis Memorial Park and all of Metropolis gathers to attend the funeral, even Superman's long-time nemesis Lex Luthor. However, while Luthor is initially bitter about not killing Superman himself, he is now able to carry out his sinister plans without being thwarted by the Man of Steel. He is able to gather Superman's DNA from blood spatter at the scene of his death and uses this tissue sample to produce a clone. The Superman clone possesses all the powers of the original and some personality aspects, but not the memories and is conditioned to serve Luthor.
Luthor sends his Superman clone to dig up the body of the real Superman so that Luthor can study it and continue to produce new clones. The clone then reveals itself to the people of Metropolis after rescuing a bus-load of children from the Toyman. While most of Metropolis rejoice over their hero's return, Lois isn't entirely convinced. Her suspicions prove to be correct after the false Superman murders Toyman to prevent him from re-offending. After this incident, all of Metropolis starts to live in fear of their "protector"; even Lex Luthor is outraged by the clone's actions and threatens to kill him if he steps out of line again. Unfortunately, the Superman clone picks up on this threat and inspects himself using his x-ray vision in a mirror, finding a small lead-lined device implanted in his brain that he suspects to contain kryptonite, his one weakness. Using his laser vision, the clone performs brain surgery on himself and removes the device.
Meanwhile, the real Superman's body disappears from Luthor's lab, recovered by a robot caretaker from Superman's Fortress of Solitude. The robot revives Superman and explains that he was not truly dead; he had slipped into a comatose state following the fight with Doomsday and was ever-so-slowly healing. The robot informs Kal-El of everything that has transpired in Metropolis since the Doomsday incident and tells him about the murderous streak of Luthor's Super-clone. Superman decides that he needs to get back to Metropolis right away, but his strength has not fully returned. The robot provides Superman with a weapon from the Fortress archives: a "kryptonite gun" made by Luthor years ago with a lead-lined cartridge.
When Superman returns to Metropolis, he finds that his double has attempted to kill Luthor and is attacking the US military. The two Supermen fight it out, but the original is outmatched since he hasn't fully healed yet. During the fight, Superman drops the kryptonite gun, but Lois picks it up and follows the two Supermen across the city. The battle is taken to Superman Memorial Park and Lois fires on the clone, who retaliates by swatting the weapon from her hand and breaking it. The cartridge falls into a pool of oil spilled from a ruptured tanker truck and as the Supermen fight, they roll around in the oil and the cartridge sticks to the clone's suit. Superman then uses his heat vision to blast the lead cartridge and release the kryptonite. The kryptonite sample explodes into a fine mist that the clone inhales, fatally poisoning him.