How about the 50s Beast With Five Fingers? I saw it as a kid and it kept me up at nights.
Best this; best that. Scariest? There are so many that I would put in the same best/scariest category. Of course, the Exorcist is both just as Beast is also.
"Generosity. That was my first mistake." "Experience must be our only guide; reason may mislead us." "Instagram is Twitter for people who can't read."