Undisputed III: Redemption
As the upcoming Escape Plan proves, there's a great action subgenre out there centered around brutal prisons. Van Damme and Stallone have been in a couple of them each. But the best is Undisputed III: Redemption, in which Scott Adkins beats the hell out of everyone in a prison fighting tournament. After winning, he is supposed to be shot by some guards but gets saved in the last moment by his pal Turbo, who escaped prison the old-fashioned way earlier in the film. It's awesome.