Not a monster, but I do remember a scary movie called Black Sabbath. It was a few short scary stories, with Boris Karloff serving the role of the MC who introduced each of them, kind of like Alfred Hitchcock did with his mysteries. That movie scared the crap out of me, I was about 10 at the time. Today I'd probably wonder what was so scary and think it was corny, but at the time it was the scariest thing I had ever seen. We had these Saturday matinees at a theater that accepted six RC Cola bottle caps as the price of admission. About 1967, I guess.