How about Frankenhooker, Carrie, Tiffany from Bride of Chucky... I'm sure there are more.

I vote for the old Satan worshiping lady who is Mia Farrow's neighbor in Rosemary's Baby

I would have to say the giant naked grandma at the end of the dead alive would have to be one of scariest things i've ever seen. i mean massive nude senior citizen, think about it.