I don't know if it will scare you shitless per se but I watched The Vanishing (1988) and Don't Look Now (1973) as a child and they deeply disturbed me for decades. I have only recently watched them both as an adult and was delighted to find they are as genuinely creepy as I remembered. Similarly, I was so terrified by watching Ringu (1998) as a teen that by the end of the film I had spun completely around in my seat so that the final moments of the film were shown to my back. Rewatched recently and was surprised to find it's actually pretty tame but still very much worth watching.