I see how it works. She wants chainsaw's power, but she can't control it. However, she can revive devils that were killed and control them. The plan was to bring him out fully, kill him, revive him and you have chainsaw on a leash.
I don't think torturing the guy is the most practical solution. I think I'd rather look into how to start moving this 10 billion people queue into the world.
So, the issue, if I understood it correctly, is that professor blocked 10 billion people from getting into the arc to let him simp for his childhood crush.
So a guy who developed no social skills starts bullying a girl he develops a crush for. Only after being confronted he noticed his absurd train of thought and seems regretful.
Bash his skull in with a brick, such scum can not be allowed to live. /s