Normally a Soft R (In my country we have Mature 15+, which sounds about right), but if it was a movie and you actually had to show the violent stuff on camera, it would be NC-17 or banned. If I were directing it, I would have the more horrific stuff happen off-screen.
I was at a game somewhat recently where it took me a while to work out that everybody had dropped acid IRL. That was interesting. It was a horror themed game and the idea appeared to be trying to mix a (bad?) trip with a scary RPG. Everybody was fully invested, so they must have got the dosage right. Lights were low, ambient noise and music was on-point.
It was definitely "Refused Classification" even despite the drug use. The PCs self-mutiliated constantly, some of them had to do so to gain their normal powers, some to remove arcane infections, some to seal pacts with Greater Old Ones. It was pretty messed up and I was sober. I'm puzzled by people that would come so close to a bad trip on purpose.
en.wikipedia.org
