User blog comment:DarkClaw3/PE Proposal: Joker (Under the Red Hood)/@comment-26454535-20200123061017

Joker was introduced by killing Jason (he was about 16 at the time so it counts as child murder). It certainly didn't help his case when he joked about killing him later in the movie. Also Jason seemed to hint at the idea that he did cripple Barbara Gordon in this version. All that considered I'd say yes, he qualifies