Serial killer in the army

Are there any movies which explores this scenario ? psychopath with the tendencies to kill people enlists in the army and kill people for fun/pleasure ?

Full Metal Jacket, maybe?

Not quite “serial killer” but DePalma’s films Redacted and Casualties of War both deal with sadistic rapes and murders at the hands of soldiers and the violent attempts to cover up their actions.

Also, the opening of Universal Soldier deals with the concept and is the origin for Dolph’s cyborg villain.