Why so much hate? their were hints throughout the story that showed how the ML to slowly despise the FL...
He never received motherly affection and the first time he experienced it he quickly realized it fell short (seeing the FL's mom protect the FL instinctive while his "mother" ordered others to protect him) he even acknowledges this as immature but it's what he honestly felt as a child who is lonely and traumatized.
You can see the people surrounding the ML throughout his life purposely praise the FL in hopes he will despise her over time and call off the engagement.
Also their are hints that both the FL and ML were slowly poisoned throughout their time together and part of the side effects were aggression and emotional instability. You also see this as he regrets isolating himself when the FL and the dukes that supported him were gone.
It's not like I don't have other criticisms but saying the endgame is so awful that it ruins the whole story is weird considering how the author let us slowly digest the multiple factors to their ruined relationship. The characters felt flawed and human.