This film is probably scary for impressionable teenagers, because it certainly isn't for mature audiences. There are descriptions of suicide, lots of blood, slashed skin, stabbing, dead bodies, burning bodies, a man is buried alive (but escapes), shooting, demonic possession and all that stuff.
The Nun 2 is rated R by the MPAA for violent content and some terror. Violence: People are burned, beaten, and thrown into hard objects, sometimes fatally.