Like you I got to this point, but only after decades of counselling and deep deep self examination. The fact that my stepfather was slowly dying (prostate cancer) and also had awareness that he had dementia (it really fuckin' scared him) left him in exactly the same terrified, powerless position he put me in, as a child. Only for me the child it was so much worse, obviously.
Talk about Karma in action? Having said this it really gave me no pleasure at all to see him like this, or to know that he was having all of these awfully frightening thoughts and feelings. Again, it too so ling to get to that point.
I don't want to focus on my situation too much as this thread is about the OP, but in time you'll feel comfortable having these feelings, not angry at yourself. It's ok to feel hatred, it's a way to survive. Imagine if you had to hold all of it in, or had to force yourself to think good thoughts about someone who had hurt you in every way imaginable, you'd go mad.
So embrace all of the feelings, good and bad, at least, unlike this man, feelings won't kill anyone. Sending you so much love and loads of hugs, sweetheart.
Munchy.
XXX