Why not 0-harm? If I remember right, the moves says you can have the damage be as low as you want, so 0-harm should be good for it.
Frex, I might have a gun, there may be a battle, and there may be a guy running away from me. I seize his ability to run away. I do zero harm, but instead shoot a rock in a way that would make him trip...
Or, I go aggro and put a shotgun to a guy's head and tell him I'll shoot him if he doesn't tell me stuff. He doesn't tell me stuff, I don't shoot him. I don't even kick him in the balls. Why not? Because I'm disciplined.
I mean, most times, I don't see why you would want to do 0-harm instead of s-harm... But there's nothing on the lid that says you can't, right?