Dark Forces #1 Your Knife, My Heart (original) K.M. Moronova

Cameron Mortem has a problem―he can't stop killing his partners. Officially labeled clinically insane, he's also one of the most lethal assets in the Dark Forces, a brutal underground military operation built on obedience, survival, and silence. But an experimental drug has fractured his control, making him a liability whenever someone else is on the field. As punishment, he's thrown back into the Under Trials―a merciless boot camp designed to break the weak and sharpen the ruthless.