Castration without any drugs. But only if proven guilty, and especially if proven guilty of raping multiple people.

And afterwards having them sit in a plain white room with a single folding chair and nothing else for at least a month. Obviously the door would be locked.

I also think that during the castration process the surgeon should repeatedly ask, "Is this okay?" And every time they scream, "No!" having the surgeon respond, "Okay, I'm glad to hear this is an okay thing to do." Or something along those lines.

And ideally the people who were raped could then be given metal baseball bats and beat the living shit out of them. I feel like that would help ease some of the PTSD that rape causes to victims.