If I understand correctly, she didn’t actually cut his balls off. Why not? She didn’t have a problem with basically causing his death, and she seemed to want him to suffer.
IIRC, she drives him to suicide. If she cuts his balls off there would be a homicide investigation (I think this is the right movie).
That was one really weird movie. Fascinating. Could not turn it off even as my nuts shriveled and crawled back into my body for protection.
Which is NOT the typical male reaction to Ellen Page now! L
The movie was already is progress when I came in. I watched for a while & thought “I am totally on her side but I really don’t want to see this.”
Yeah, but you don’t want to piss her off! 
Interesting idea from the investigation angle. However, I think she’s got a good point that once the authority discovers that he is a paedophile, they probably won’t be doing their best going after the killer.
I thought the point was to mind f*ck him into committing suicide and then leave without a trace. Recent surgery would certainly leave a trace.
Also it made it a worse mindfuck to make him think she did it and NOT do it–a violation and feeling of total helplessness like that of his victims, he found himself utterly at her mercy, debased and begging. She could actually do it to him at any time, but in theory, having something to lose would give him motivation to give her what she wanted in hopes of ending the ordeal. But it wasn’t enough. Like when the victim cooperates and they still mutilate/kill her–the betrayal and degradation of hope is a sadistic element. At least, even manipulated, he chose to end his life, she didn’t just do all that and kill him and stage it as a suicide. That and the revenge factor makes her still the hero, even in a twisted way.