I don't like characters who are bullies, and I don't like characters who have entitlement complexes. It's as simple as that.
I never liked Severus Snape because he tormented innocent children over whom he held authority, and because he believed Lily owed it to him to return his feelings, even after she stopped being friends with him, even after she married someone else, even after she died. I can't entirely sympathize with Erik because he believed he deserved to have Christine, even if that meant deceiving her, manipulating her, and forcing her to stay with him for the rest of her life. On the other hand, I love Holden Caulfield because while he had a very cynical view of most things, he didn't believe he deserved to have anything meaningful in his life.
I never liked Severus Snape because he tormented innocent children over whom he held authority, and because he believed Lily owed it to him to return his feelings, even after she stopped being friends with him, even after she married someone else, even after she died. I can't entirely sympathize with Erik because he believed he deserved to have Christine, even if that meant deceiving her, manipulating her, and forcing her to stay with him for the rest of her life. On the other hand, I love Holden Caulfield because while he had a very cynical view of most things, he didn't believe he deserved to have anything meaningful in his life.