Quoted from KozMckPinball:The most disturbing horror movie I've seen was Hostel. Not a date movie by any means but the movie premise is plausible and pretty sickening because of that. I kind of hate that I am promoting it here.
I've always been a huge fan of horror movies since the 80's. After watching Hostel I won't watch any slasher/torture movies again. That movie was just sickening.