YMMV: The Nail
- Moral Event Horizon:
- Joker takes a running leap over this when he murders Dick/Robin and Babs/Batgirl with homicidal glee. You can hardly fault Bats for killing him after that
- Jimmy Olsen crosses it when he casually murders Kal-El's Amish foster parents
- Batman having an Heroic BSOD that borders on DEH crossing after the deaths of Dick and Babs and his murder of The Joker is NOT funny. The ridiculous expression in his face when Alfred and Selina try to make him react is, though.
- Selina dressing up as Robin to try and get him to come to terms with himself could also count
- Sequelitis: Another Nail.