For films that have (brief) moments of sheer horror/terror, I can only think of a few:IS there such a thing as a truly scary horror film? Seems like it's all just meant to scare kids.
Chakushin Ari (English title: Last Call) - The Japanese original had at least one (subjectively) terrifying moment where an apparition was walking, upside-down along the ceiling of a hallway, from background to foreground, approaching the unsuspecting protagonist. The apparition's appearance was not the standard jump scare, rather, she had a slow, deliberate gait, crossing from dim light to shadow, with her grim visage becoming more apparent as she got closer to the camera. Gives me chills just remembering it.
V/H/S (2012) - The first found footage short, "Amateur Night" was particularly disturbing. Casting for the character "Lily" was on point. This short was well written and paced.
But a truly scary horror film, from start to finish, is hard to come by.