Excuse me? Is he the one who had done JK wrong?? This is victim blaming.
But yeah, he should've had a change in character. He should be more selfish, more self centered, he should've fought for himself more. He wouldn't have had to deal with that old perv or JK himself.
But if you think he is the reason this manga is problmatic because he is kind hearted? You should revisit your mindset.
In the end jk is a black flag character who author somehow decided to give a cliché redemption arc. But he is still a bad person. He let his past define him his whole life but love somehow made him develop empathy like?? Still this is better than nothing. What does kim dan achive as a person this whole manhwa tell me. I can accept him forgiving jk but i just can't accept him ending up with jk. Sorry.
A good main character* also you can't measure someones kindness by how much they forgive. Is someone who isn't kind to themselves truly kind, or is it just comforting for them to please others? I might seem like I'm blaming Kim Dan for the whole problem, but I realize it's not entirely his fault. I'm not saying any character is better than another. All I mean is that even a bad character like JK showed some development, while Kim Dan, one of the main characters, was only given devaluation under the guise of kindness. And that's one of the reasons I find this manhwa bad.

Just realized it isn't jaekyung that makes this story bad, it's kim dan. Like wdym we both weren't perfect. Yes y'all not perfect buttt at the very least jk had a sembalance of character development, kim dan on the other hand got the rofan shojo manga female lead bella swan treatment, zero character development.