He didn't get a bad ending. A bad ending for him would be that he were to be forgiven by chiwoo and given another chance. A good ending is he going to therapy, is he learning Al the things he is missing, emphaty love. That is a good ending for him. Not for him to continue on the path he was on. For his actions to have no consequence would mean he doesn't need to change but if he wants a happy ending, he needs to change.
This reminds me of bojack, horseman, of course
Because nobody wants to see a rapist get an happy ending. This is not about having flaws or having imperfections at all... Did you know that a lot of famous serial killers have been abused by their family too? It could explain why they became like this... but this is still not a reason to pity him more than necessary. You said that Jihyun is a victim and I agree, but Chiwoo is too? Why do you seem to pity Jihyun more than Chiwoo?
Also, his end was not that bad since he's not in jail and have a chance to start over? What more do you want? Chiwoo staying friend with him? But that would be a happy ending for Jihyun only not Chiwoo who has been traumatized by what he did to him. No I'm sorry but Jihyun had a pretty ok ending.
And I want to add that it's not true that there aren't much story where characters who are imperfect don't have their happy ending... They're a lot out there since people tend to love more problematic characters than the nice one
I often wonder why does the "good" almost perfect guy gets the happy ending? How about those represents Jihyun? U know.. those with imperfections.. I mean, Idk.. I really feel bad for him. Growing up without guidance and affection from his family. Then he finally found someone he truly cares for.. it just sucks.. coz I think he's also a victim (atleast thats how i felt) ? :( Ofcourse, violence is a no no but I wish he couldve got a happy ending.. :(