A bit of history about the universe of Dc comics in the series Blade Part 1:

On Earth 1502, the Justice League was like nothing in the Hall of Justice when Superman came out of nowhere, leaving the entire league shocked as he looked weird. The Joker had used a hallucinogenic gas that caused Superman to see the entire league as if they were Doomsday. This got to the point that Batman had to assassinate Superman. Batman did not want to kill Superman but had to do it since Superman had killed several members of the Justice League, among these members were Falcon Man, Black Lightning, Wonder Girl, Red Tornado and Plastic Man. And also several members of the Teen Titans who went to help the league. The members who died were Nightwing, Kid Flash, Arsenal. Other members did not die, but they were very injured, such as Green Arrow who lost his arm and Shazam lost his tongue which prevents him from transforming back into Billy Batson.