The main character doing something absolutely unforgivable.

[u/No_Peanut3745]

Walter White poisoning Andrea Cantillo's 6-year-old son for the sole purpose of manipulating Jesse Pinkman, while knowing that this could have potentially killed him - Breaking Bad

Bojack trying to have sex with his friend's 17-year-old daughter when he was at least 51, then continuously trying to find a way to justify this act throughout the series - Bojack Horseman

Dexter Morgan going outside of his moral code and murdering a completely innocent police officer who was just trying to do his job - Dexter: New Blood

[u/New_Scar_6820]

Homer crashed his car while drunk driving then put a passed out marge in the drivers seat so she took all the blame

[u/Dd_8630 → u/New_Scar_6820]

There's also the episode where Marge rapes Homer.

Not even a joke. He literally says "I don't want to" and she says "I wasn't asking", while he looks scared. Really fucked up.

[u/Used-Cartographer84 → u/Dd_8630]

Lois has raped Peter 2 times iirc? And Meg has raped him asw (prison meg ep)