It’s never an entire movie, it’s a scene here and there.
Like in The Exorcist, when they showed it on network television back in the late-70s it must have been, the CBS Saturday Night Movie or something like that, “viewer discretion is advised”.
Anyway… clicking channels, I stumbled upon a moment during the ritual itself, with the girl in silhouette on her knees, arms towards the ceiling, the demon Pazuzu behind her. That screwed up many a night afterwards.
As a young adult, another scene that fucked with my head for many a night was the grainy dream transmission, with the faint audio covered in static noise, from John Carpenter’s “Prince Of Darkness”.
Now I’m gonna flip the concept on its’ head and tell you what film cured my fears of the dark at the time. Martin Scorsese’s “The Last Temptation Of Christ”.
Mine would have to be Hollow man (2000) it was on TV at the time and for some reason as a kid watching the shifting both the animal and the human scene where they turn invisible where the skin disappeared then his muscles and veins, was absolutely terrifying, I don’t remember well but my parents said I wouldn’t let them sleep for weeks.
Tbh I don’t think anyone is old enough to watch Mars Attacks. The visual design is too much. The movie itself isn’t that bad, but the fucking martians. Fuck me.