Betes backstroy is tragic, yes.
He is also a complete douchebag, yes.
I get where the author is aiming though, he's an unlikeable dick because he's afraid of getting close to people again, clearly and is pushing them away.
It doesn't justify his behaviour by any means, but it's at least...
@HDMI1 That depends on lore, in mythology the Dulahan is a fairy, not undead so it would be the lich of a Dulahan in that case.
Of course many examples of media they are undead knights and/or haunted armour so I certainly get your point too.
Everyone getting mad he didn't shag her seems to be overlooking a few things.
Firstly that she quite openly wants his power, not him. Why chain yourself down/ give her levarage over you like that just for some action? If he just wanted sex he has that servent girl whom would no doubt comply...