Definitely an interesting watch. I think I'll be revisiting my thoughts on this movie in the future, but for now I'll just say this:
There's a unique terror found in the idea that a person could live a life so vacuous, so meaningless, that the most noteworthy thing about it was just the pain they continually caused others. Or even simply desired to cause others. After all, which is worse? To be viscerally, physically evil? Or to be spiritually and intellectually vacant, a kind of horrifying philosophical zombie?
In a way, I think it's a question the movie decides to leave for the viewer.