Hand to hand combat is mostly used throughout. Minor blood injuries are visible sometimes.
A man is hit in the head with a beer bottle, he then turns around and stabs the person who hit him in the head. We get a brief glimpse of the wound through the persons shirt, and it dampens where the stab was.
Two men fight in prison, one stabs the other (blood not visible) the stabbed man grabs the knife and throws it somewhere else and then holds him down and somewhat offscreen curb stomps him causing the mans teeth to break. (Minor blood seen coming out of the man's mouth)
There's a brutal fight between one man and a group of men in a prison courtyard, and the man beats most of them.
A man fights with a group of people in a prison cafeteria. He hits them with his tray and kicks one of them onto a table (No injuries shown) he then grabs a bottle of what appears to be napalm and throws it on one of the attackers.
A man takes down two security guards by beating them up. (They live)
While two men are fighting, one grabs a hammer and hits the others hand with it. Minor blood visible. From a camera view much much father away, we see the man who was holding the hammer repeatedly hit something on the floor (presumably the other man) (We do not see the man being repeatedly hit with the hammer.)
The top half of a man's head is graphically blown off with a shotgun. This scene is completely shown onscreen with his body shown twitching with blood pooling out from his destroyed head.
R: Graphic violence and Gore.