The graphic novel “Kingdom Come” dealt with that in an interesting way. Superman has an almost sidekick/partner named Magog. So the Joker gets loose again and kills over 100 people, and it is heavily implied that one of those people was Lois Lane. Superman takes Joker into custody. Magog just goes up to Joker, who was, at that time, not a threat, and just murders him on the spot. Superman arrests Magog and is devastated when Magog is hailed as a hero and is acquitted at trial.
Even if you aren’t a comic book fan, its a wonderful read.
Totally agree. KC is one of the best graphic novels I’ve ever read. I’m quoting imperfectly, but it’s been said if you were given superpowers, Marvel is the kind of hero you’d be but DC is the kind of hero you’d aspire to be.