If your a man, watch The Hunt. Don't read anything about it, just jump in. Its on netflix.
I've seen damn near every horror and thriller movie, and this one got me. It's not a horror movie technically, but it will fucking scare you. It's also just a damn fantastically made movie. 93% on rt.
Other than that, Martyrs. Do it, pussy.
Last nomination for right now, Shutter. The original one, not the american remake. One of the scariest movies I've ever seen.
Ill go ahead and throw out The Descent even though most people have seen it by now. Awesome.
In my opinion all of those movies are the highest of top tier when it comes to being genuinely disturbed with out any silly jump scares.
Alright last one. Eden Lake. Genuinely scary because its a more realistic and plausible scenario that could happen to anyone.