I've heard most Japanese horror is pretty f*cked up. The Ring is a remake of a Japanese original.
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Of recent years I’d say the first Paranormal activity is genuinely scary. Not many films are actually scary but that got me.
Martyrs, the original french version very disturbing
I found the first Sinister to be very good
Just been ranked the best by average heart rate. Still not seen it yet.
https://www.nme.com/news/film/new-study-ranks-scariest-horror-films-by-average-heart-rate-2791307