“ | Several years ago, the Joker had set off one of his deadly laughing gas bombs in the Daily Planet's offices. It created a terrible green cloud outside the building. Everyone inside was killed in seconds. That startling grimace was etched on all of my friends' faces. Only one person survived the attack... ...and tried to take on the attacker. I was thousands of miles away at the time... Desperately speeding my way there as fast as I could... ...while the Joker crushed my wife's skull. | „ |
~ Superman recounting the Joker's attack on the Daily Planet. |
The Joker is the overarching antagonist of the 1996 DC four-issue comic miniseries Kingdom Come. He is an infamous clown-like supervillain and terrorist, who is the long-time archenemy of Batman and is the most dangerous and notorious criminal in Gotham City. He launched a terroristic attack on the Daily Planet in Metropolis that resulted in the death of Lois Lane and the entirety of the newspaper's staff, which drove the anti-hero Magog to kill him in an act of vengeance, thus setting the events of the miniseries into motion.
Biography[]

The Joker attacking the Daily Planet before killing Lois Lane.
Several years ago prior to the events of the miniseries, the Joker travelled to Metropolis and broke into the offices of the city's newspaper, the Daily Planet, where he launched a deadly attack, in which he massacred the entire staff, including photojournalist Jimmy Olsen, with his laughing gas bombs. This created a giant green cloud of gas that can even be seen from afar. Though it looked like all the employees were killed, however, reporter Lois Lane, Superman's wife, was able to survive, as she wore a gas mask to prevent herself from inhaling the Joker's gas. Though she tried to fight the Joker off, he smashed her skull with her own nameplate, which he got from her desk.
Though Superman had flown as fast as he could to try and thwart the Joker's attack, unfortunately, he was too late. After sucking in the gas, he was horrified to find a dying Lois, who encourages him to not take his revenge out on the Joker so as to not lose his humanity. Honoring her last words, Superman captures the Joker and turns him over to the authorities, but before they could take him away, Magog, a violent anti-hero, suddenly arrives and kills the Joker in an act of vigilante justice, thus avenging the death of Lois and all the other Daily Planet employees.
Legacy[]

Magog was praised for killing the Joker, allowing him to be acquitted of his crime.
The Joker's attack on the Daily Planet had a negative effect on the reputation of superheroes, as the general public by had now grown weary of supervillains and prefer to have them killed so that they won't continue terrorizing more innocents; Following his killing of the Joker, Magog turned himself in, however, he was unexpectedly acquitted when his act had garnered mass support from the general public, which forced many other superheroes, including Superman and Wonder Woman, to retire or go into exile. Thus, the actions of both the Joker and Magog had influenced a shift of public opinion on superheroes and a drastic change to the concept of heroism, bringing forth a new generation of metahuman anti-heroes or rather self-proclaimed "protectors", who admired and revered Magog, to the point of even following his footsteps in assuming a violent approach in fighting and eliminating crime and supervillains.
However, this had immense consequences, as their chaotic and reckless attempts at protecting Earth and their branding of justice only brought existential despair and hopelessness amongst humankind instead of hope. The last straw was when Magog caused a nuclear holocaust in Kansas, Texas, which drove the United Nations to plot to kill all metahumans through nuclear bombing while Superman and other past superheroes returned to regulate the metahuman community.