Ending was sort of disappointing.
First time I've seen it and I have to say that it's an incredible film or even, dare I say, documentary-like about a correctional facility and how it works there. Now, that last fight between the two really looked like only one would be getting out alive and although both survived it would have been better if O'Brien had killed off Moreno as he raped O'Brien's girlfriend and he'd have to look over his shoulder whenever he'd get out too.
Someone might say "well, O'Brien killed his brother" but you need to remember that was a tragic accident whereas Moreno planned to rape J.C. so it's not the same thing.
Btw, it was a relief when Horowitz read that Tweety got wasted and his partner had the radio explode in front of him, albeit it didn't finish him but his hearing and vision probably got badly damaged (definitely the hearing).