Kill 'em All (2013) 斩尽杀绝

Captured international assassins are locked up inside a high-tech bunker known as the Killing Chamber. To break out of this concrete hell they must duel each other, fight deadly ninjas and battle against gangs of masked maniacs. And... if they survive this, they will have to confront Snakehead: the lethal, deranged top dog who will stop at nothing to kill 'em all!