From Ivan the Terrible, infamous for having beaten his own son to death, to Saddam Hussein, responsible for poison gas attacks on his own people, here are the stories of history's most ruthless tyrants.From the Roman Empire to the present day, including General Pinochet, Ida Amin, Pol Pot, Hitler, Stalin, Mao, Caligula, Enver Hoxha, Jean Bedel Bokassa, Nicolae Ceausescu and Than Shwe.