I'm a bit of a wuss when it comes to scary stuff (for the longest time I played minecraft on peaceful because the idea of being snuk up on by a creeper was to scary) and I couldn't watch a full youtube playthrough.
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Have you ever seen the movie "The Mist"? I think they are of comparable amounts of horror.
I didn't think the mist was that scary, but they should definitely conjure up some more movies based off of Stephen King's novels. "The Stand" preferably.
There do exist adaptations of The Stand, and I believe that another is in the works.
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Regarding Amnesia, I've heard similar tales of horror. As with all horror games, though, playing it with someone else in the room will make it less scary.