Silence of the Lambs! Used to NEVER watch anything scary but turned this on in the middle of the night back when you did not have an on screen guide to see what it was and got hooked on it and couldn't stop watching. I was living alone at the time and didn't sleep well for days after! It did not help that I fit the profile of his chosen victims to a tee. Now that would be an easy one to take. The movies now are much more graphic and bloody.
OH, yeah- In Cold Blood was the scariest movie I've ever seen. Because it shows sociopaths at their best- Perry had some sort of morals- you shouldn't rape a young girl before you killed her- killing her was OK. That's true evil- not supernatural bad guys- human beings.
Ive always been fascinated by the Manson murders. I could never figure out the hold he had on those people, especially the girls. It probably had a lot to do with my age at the time. The Beach Boys and Doris Days son. The man got around.
It seems when you're a predator, you sense your prey- lost, unhappy teenagers, rebelling against their parents- As far as the guys, he had connections for drugs, and evidently was charismatic, like most psychopaths- Look at Ted Bundy-