Gary Vinter, in prison for double murder, stabs a fellow inmate in the eye and gives another brain damage.

James "Porky" O'Rourke's addiction to violence means he is one of the most feared men in the UK prison system.

One of the UK's most infamous serial killers, Joanna Dennehy brutally stabbed three men to death.

Covered in tattoos, his terrifying appearance makes Jaime Osuna a feared man in the U.S. prison system; awaiting trial, he begins practicing Satanism and attempts to kill a fellow inmate.

Edward Johnson was sent to prison for the brutal murder of a female friend, but the violence didn't end there.

James Robertson is one of the most feared men in the US prison system; he murdered his cellmate, attacked a prison employee and doesn't hold back from getting what he wants.