Title Superman: What Ever Happened to the Man of Tomorrow
Format miniseries
Binding standard comic
Date September 1986
Writer(s) Alan Moore
Artist(s) Curt Swan, George Perez, Kurt Schaffenberger
Collects Superman 423; Action 583
Storyline

Superman 423
Lois Elliot (formerly Lane) welcomed a guest into her home. The Daily Planet's Tim Crane interviewed her for his piece on the last days of Superman.
Superman, with the bulk of his villains dead, began working for the government. Upon returning from one of his missions, Superman was told Bizarro was loose in Metropolis. Bizarro told him he was trying to be a better imperfect duplicate - he'd blown up Bizarro World and come to Earth as an adult (opposite of Superman). He then pulled out some blue Kryptonite to kill Superman (again, opposite: one alive, one dead), but he killed himself instead.
Next, Toyman and Prankster outted Clark Kent. They'd gotten his secret identity from Pete Ross, then they killed him. Kent was outted when they mailed him Ross's body and a box full of Superman toys, which went on a rampage. While doing an on-air TV newscast, Kent's clothes (all but his outfit) were burned away by their heat vision.
Superman gave up his secret identity and wondered why his "nuisance" villains were now killing.
Lex Luthor had found Brainiac's head and it had adhered itself to him.
Hundreds of people turned into Metallo and attacked the Daily Planet. After defeating them and getting them to authorities, Superman took all the people who were close to him to his Fortress of Solitude, where he could guard them. After everyone was safe, the Brainiac - Luthor team captured the Kryptonite Man and headed to the North Pole.
That night, Krypto, who'd been patrolling the galaxy, returned. After everyone was in bed, the Legion of Superheroes - and Supergirl - arrived for a visit. Kara was visiting the 30th century when they'd decided for a time travel trip.
Brainiac gave him a statue and admitted they were paying their last respects.

Action 583
Superman destroyed his giant key so no one could harm his loved ones. Brianiac - Luthor arrived with the Kryptonite Man. As they prepared a plan, the Legion of Supervillains arrived from the future. Brainiac - Luthor put up a force field around his ship and the Fortress. Though heroes arrived (Batman, Robin, Captain Marvel, Wonder Woman, Martian Manhunter, Green Arrow, and Hawkman), no one could penetrate it. After an assault, the villains gave up for the night.
Jimmy Olsen drank a container of Elasic Lad serum while Lana Lang bathed in the waters that would turn give her powers. They decked out in costumes found in Superman's trophy room and attacked the evils waiting outside. They were both killed, though Lana killed Luthor and Jimmy took out their generator. Strangely enough, the forcefield stayed on; Brainiac reanimated Luthor's body. A full on attack on the Fortress began. Krypto was killed defeating the Kryptonite Man.
With Superman on the rampage, the Legion of Supervillains escaped back to their own time. Brainiac could no longer control Luthor's body. His head came loose and walked toward Superman before he, too, died.
Superman realized he'd gone up against all of his foes except for Mxyzptlk. The fifth-dimension sorcerer appeared to them in his true form, as a monster. Superman realized what he was holding in the statue the Legion had given him - the Phantom Ray. He blasted Mxyzptlk with it as he said his own name backwards. The creature was killed - pulled apart by two dimensions.
Superman, realizing he'd meant to kill, walked into his gold Kryptonite vault. The heroes, with the forcefield now down (Mxyzptlk had been keeping it up) entered. They found nothing in the vault except for a secret passage. Superman had given up his powers and wandered into the cold. No body was ever found.
After the interview was over, Lois's husband brought their child in to play. The infant grabbed a piece of charcoal and smashed it into a diamond.
Clark closed the door and went back inside with his wife.


Notes, references to time, and chronology:
Supergirl is dead (presumably from CoIE) at the time of this story.
The date August 16, 1997 was noted by the interviewer - it was the 10th anniversary of Superman's death.