Superman killed the Joker. That is the event the entire Injustice universe is built on — the specific catastrophe that turned the world's most principled superhero into its most dangerous authoritarian. He did not lose the war against crime. He won it, in the most permanent way available, and in doing so lost the thing that made the winning meaningful. The reason for the fighting was not just protecting people. It was the belief that the methods of protection mattered as much as the protection itself.

The first session establishes the two Supermen — the alternate-earth dictator and the Justice League Superman who has come to stop him — as the organizing frame for the game's political argument. Absolute power does not corrupt absolutely. It reveals what was always there, waiting for the cost of the old restraints to become higher than the person was willing to pay.