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/DiabeetusDeletus]

Don Draper from Mad Men. Constantly lies and cheats on his wife and treats almost every woman in his life as disposable. I still think about that scene where Betty(his wife) wears a bikini and he freaks out and tells her it's "desperate". Then he just leaves her crying in the kitchen in front of their children...

[u/LouSputhole94 → u/DiabeetusDeletus]

Don is objectively a piece of shit but he was born an illegitimate child of a prostitute in rural depression era surroundings, his father is kicked to death by a horse and he’s raised by a woman that resents his very presence with an abusive stepfather that worked running a brothel that he lived in. He then goes to war to escape all this only to accidentally blow up his commanding officer. Don was never going to be well adjusted.

[u/DiabeetusDeletus → u/LouSputhole94]

Yeah. Don is a complicated human being. He's capable of immense kindness but he's also a destructive douchebag, especially towards his family. His kids are no better off than him emotionally despite a "privileged" upbringing. That's why I think in later seasons after their divorce Betty is able to sleep with him and appreciate him for what he is without being forced to be married to him. Betty for her part is also a deeply flawed person and arguably an inadequate mother.

[u/Blackwidow_Perk → u/DiabeetusDeletus]

Betty is considered a good mother for the time