
but what would happen if you fell in a hole with no love since birth, always pressured and thinking that you didn't do good enough, and blinded by despair? obviously that's how a child would react if they never got any love nor being praised by their own parents for something they did. it feels meaningless.

SPOILERS
So basically he was envious of her and jealous and stuff but he didn't treat her like shit and abused her out of his own will. Jieun poisoned him which made him go haywire and like, controlled him in a sense? Which is why he acted like that towards the FL. The ML didn't even kill the FL's dad in their past life as well as I've gathered. Apparently he thought he could use him to keep the FL close? Anyways during execution day the ML tried to stop the FL from getting killed but bitch face Jieun (who dresses worse than Trashta I mean seriously-) stopped him and held him back.
Overall it's just stupid the author justified whatever the ML did by saying "oh he was being controlled, he wasn't acting on his free will because of the poison Jieun gave her" which is kinda a half assed story building thing ngl
I also think people are forgetting that this is the second timeline--wayyyyy before this guy even started abusing her and treated her like shit (which was apparently the result of a poison).

He was a child... with no one guiding and teaching him what the right morals were; even loving him.. They were just there watching him overwork himself. That easly grew to be hatred and all that. I have seen so many cases in real life where people suffered, as children, from a tribial matter -to me- and they become traumatized or full of recentment just for that. But that doesnt take away any importance from what they felt right then.
So u treated her so badly because of jealousy .....that's so pathetic...