SPOILERS: the film ends with the man kept in a cage, and disfigured. It is implied he agreed to stay and suffer abuse so she wouldnt hurt others. The women also returns to a cheating parter.
It’s not diagnosed or discussed in the movie, but it can be assumed that a character who killed for fun and hallucinates people who are not there is mentally ill.
There’s a scene where someone talks about how you can’t put a great white shark in an aquarium because it’ll bash itself against the glass to harm itself, but there are no actual sharks in the movie.
No incarceration, but much of the movie takes place at an animal shelter which can give similar vibes. Additionally, a woman is kept in a cage that would be used for large dogs.
A dog who is neither sick nor violent is euthanized by injection. They do not show it dying or suffering, but it is taken to be cremated in a plastic bag. This scene happens very early in the movie.
Dismembered body is fed to dogs in an animal shelter. Aftermath of the dismemberment results bloody floors and people. Teeth removed, someone cuts off their own finger. Seth is horribly disfigured in the closing scene.