Oh! Is it the Shinra guards? You can 'pay' by fighting them, even though they aren't too tough. (The ones after you get off the elevator.) However, you can go 'bankrupt' by fighting so many times that you actually kill them.( It happened to me, I sucked at dodging their sight.)
Or maybe it has something to do with the submarine guards? You can choose to kill them, or not.
These are just thoughts though...
