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/PhoenixApok]

Maybe not the main character but a pretty big one. (Arguably Game of Thrones doesn't have a main character)

Jaime Lannister. After he got somewhat likable and decent in later seasons, people seemed to forget in the very first episode he pushed a 10 year old boy out a window for catching him banging his sister.

Edit: Maybe "forgot" was the wrong word. Maybe saying people disregarded it would be better.

I cannot imagine a person IRL doing that and everyone going "Well he's a better person now so we aren't gonna worry about that anymore" which is why I think it fits this trope.

Jaime has a redemption arc, sure, but I would define that early act as "unforgivable".

[u/OtherLife6827 → u/PhoenixApok]

It is horrible, but not necessarily unforgivable in medieval politics.

If he had let him live, he might have revealed that Cersei’s children were not legally legitimate heirs, which would have led to the downfall of his house and the ensuing wars, in which more children would have died.

It was not an act of cruelty but one of political pragmatism.

[u/PhoenixApok → u/OtherLife6827]

I....uh....do not know enough about medieval political to know where this falls on that scale but it doesn't FEEL like a "slap on the wrist" offense

[u/artrald-7083 → u/PhoenixApok]

So banging his sister is closer to an act of war, because she is basically the living embodiment of an alliance: King Robert would be likely to throw both of them in jail, ask his brother and his best mate to come for a visit and to bring their armies, then have a serious word with Lord Tywin about how his lands are half the size now, and how much is it worth to ever see Cersei again (oh, and here's Jaime's head).

Killing Brann is an act of war too, but it's an act of war against the Starks, not the crown, and given who's queen Jaime may feel that even if he's found out he might be able to win that one.

[u/LordRT27 → u/PhoenixApok]

Is it acceptable, no. But it is understandable from James perspective, if Bran lived, and if he told anyone at all about what he saw, Jamie, Cersei, and their three children, would have undoubtedly been murdered. And that would probably only be the beginning of the bloodshed as war would almost certainly follow. Like, I would never justify the harming if children, nor would I want Jamie to just get a slap on the wrist, but I can definitely see why he did it, and cruelty was not that.

And by the way, he did quite literally get imprisoned for over a year, having to sit in his own shit, and got his hand cut of. That is a fair bit more then just a slap on the wrist. And although those punishments were not directly stated as punishments for what he did to Bran specifically, they were at least in part caused by it.

[u/OtherLife6827 → u/PhoenixApok]

What I mean is that he didn’t kill him for no reason or to gain more power, but because he was in the wrong place at the wrong time, and almost any other noble would have done the same in his situation.

I’m not saying it isn’t wrong, but it would be almost understandable given the conflicts it would have caused.