Well a dude does cut off a girl's head while he has sex with her but that's mild compared to the rest of the movie.
I watched it without knowing what I was getting into. The whole thing is scarring but then you et to the twist ending and you discover that you can in fact feel worse than you already do. They also don't spare you anything, they show you everything and make sure you see it and have to deal with it.
Oh okay, that's not the same decapitation I saw than