Responses
I think it was a mixture of disgust and resentment. His brother clearly had romantic & sexual feelings for him despite being blood-related, and the MC was treated like dirt by their father and became a slave while the brother lived a lavish life as a nobleman. Probably a whole mess of other things but yeah, I would hate the brother too ngl.
I know that the brother did bad things at the end but he was really caring through the story why did the MC hated him so much?