I saw a probably real internet vid, I think on nothingtoxic, of a guy beat a puppy to death with a brick. The disturbing part was how calm the guy was and how he wasn't happy just hitting the dog once. The first blow breaks the dog's back or neck and immobilizes it. You can hear it squeal and bawl. The guy walks around a bike rack, picks up the brick again and smashes it a couple more times and walks away like nothing happened. Also disturbing is the fact that the person on the balcony taping it says and does nothing.
I've seen Cannibal Holocaust, ToD and plenty of others listed here. I don't really find any of them too disturbing. Maybe because I knew a sick fuck in the 80's who owned a music store and had a collection of real torture/snuff films, some involving kids. Beta, vhs and film, all illegal. Curiosity makes you want to watch, then once you start it was hard to turn away.
Not disturbing at all, but pretty gory is one of my favorite movies, Dead Alive. "I kick ass for the lord!" :1orglaugh