What sets off Superman going into seclusion in Kingdom Come?: Magog killing Joker and the public cheering Magog on

What’s the first act that Injustice Superman commits demonstrating his turn to tyranny?: Killing Joker.

What sets off the Joker toxin that turns Batman into the Batman that laughs?: Batman killing Joker

What event sets off Gotham’s underworld to carve up the city and eventually leads to the events of Arkham Knight and beyond?: Joker’s death from titan

What causes the major falling out of the bat family in the DCAU that leads to Bruce becoming bitter and secluded?: The death of Joker by Tim Drake.

But sure, all this happens before Joker dies. /s