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 II, from director Michael Chaves, has received an R rating for "violent content and some terror" from the Motion Picture Association. The decision is fitting, considering Chaves described the film as The Conjuring universe's "most violent" offering.