In Detective Comics 23.2 Harley Quinn straight up explodes dozens of children with exploding video games.
No matter how much abuse she suffered at the hands of the Joker, that is a singularly irredeemable act.
I've never been able to accept Harley as a anti-hero or even hero at times after reading that issue. When we were supposed to feel bad for her in Heroes in Crisis it just fell so flat because that issue should still haunt the character.
Has DC ever addressed this issue and tried to undo it or something?