Remember he was a child when he made tht decision also he was promised that she was going to be treated nice like a family member its the woman who didnt do as she promised him n when he went back for her he was told tht she was dead
He wasn't a child anymore when he raped her after she came to the castle as a concubine, only becoming decent when he learned that she was the real Bella after all and not a look-alike. He wasn't a child either when he killed the maid who dared to tell the truth in his face about him and lied to him that Bella was dead. He clearly did not regret his actions. His true nature his that of a jerk.
Also, actions have consequences. You can't sell another human being (that is slavery by the way) for a castle and be forgiven, even if you are a "child". That is even more so when he knew what he was doing. She did told him that having a cute and pretty servant has a punshingball was the trend among nobility.
But when they made the deal she said she was going to treat bella well and back thn slavery was normal also she was his concubine n back thn woman had no right so to thm tht was normal we know is wrong but they didnt n now he is trying to make up for it
Even tho he doesn’t even know how since he has no experience
Once again, selling someone is bad, that is slavery. She was treated as an object without will, to get a castle. It is already bad in itself even if he didn't know what would happen to her (and he clearly should have know better, since he was warned contrary to what you imply). That is also forgeting how he treated her when he thought she was just a concubine and not the actual real and living FL. It showed his true colors, since he only started regretting his actions toward her when he realize that she was Bella after all. Ergo, he is a jerk who only treat her better because he fancy her. With the trauma, he is not redeemable as a love interest anymore. There is a limite to what you can make readers swallow. In the very last chapter, he is actually trying to guilt her by doing self-arm... He is getting worse, not better.
In fact, the only ending where them getting together would make sense is a "bad ending" showing just how toxic their relationship is in a "Your majesty I want you" (korean novel) style.
i’m starting to feel bad for him but then i remember what he did and he totally deserve every hurtful thing she’s doing to him. like he literally sold her off and she got abused and treated like a dog. he’s lucky she even allows him to be next to her.