So confused

It's because his ego is bruised over the fact that mc will never see him romantically. He wants mc to beg him and depend on him. The more mc refuses and becomes independent, the angrier Lister gets. He's an entitled, narcissistic pos

It's sad that he can't just get him to like him.

It's because he doesn't just want to be liked, he wants complete control of him. He doesn't see him as his equal.

But what made him flip? Was it bcz when the MC still had faculties he didn't reciprocate his feelings? Or was it always one sided or just well-hidden?!!

I think he was most likely always attracted to mc but was too 'proud' to ever admit it to him. He also most likely already knew he'd get rejected. The thing is, judging from his reaction, he's incapable of courting mc properly anyway. He's too egocentric to actually try and court someone with the possibility of a rejection. He wants him depended and weak, so he can control him like an object and since he can't achieve that, he flips because he's entitled.

We're not sure yet when the abuse started, but it seems to at least be related to "something which happened 2 years ago", around when Sylhan's madness started, because based on flashbacks, he seemed to be quite a capable person before.
At the moment, I think it has something to do with ML's promise to Sylhan, and the fact that his "punishment" as a slave might some day end and he is able to leave.
Lister also thinks Lloyd will take Sylhan away again.

We don't know yet what the promise between Lloyd, Lizbeth was yet.

I'm sure the abuse started after he'd lost his mind. My question was whether the psychosis was drug induced or a natural part of pathology. The psychosis could cause him to lose some part of his memory. So idk what happened before. According to the flashbacks they were friends when little and then something like 20 years passed? And they met again under these circumstances. Maybe his punishment as a slave isn't forever. But he seems doubtful and idk why.