Protocol 10

Protocol 10, is the last-resort/highest security method to control the criminals in Arkham City by using TYGER to kill everyone inside.

Activation
Protocol 10 can only be activated when approved by the City Council only when the inmates were able to get a hold of fire arms and appear to be attempting a mass break out. So far it appears that not many members of the Council approve of this method, hoping this protocol would never be needed to have been activated. Commissioner Gordon even voiced his disgust at the measure. Bruce Wayne learned about Protocol 10 when Hugo Strange alludes to it being nearing completion shortly after Wayne ended up incarcerated. It's also implied that the protocol was virtually unknown to most of the inmates, as the Joker, when Batman asks what Protocol 10 was under the belief that Joker was in cahoots with Strange, denies any knowledge on what it is.

Batman: Arkham City
Once it was deemed that Arkham City lost its ability to control the weapons being leaked into the city (Provided by Hugo Strange). The city council approved Protocol 10 to kill every inmate in Arkham City. Hugo devised this plan since the beginning with Ra's al Ghul to gather all of the criminals in Gotham to one place and just wipe them all out. However, Batman managed to make it to the top of Wonder Tower and stop it before the plan could be completed. However, dozens if not hundreds of inmates were killed or injured during Protocol 10.