That's an interesting question. I think you want to hurt someone enough to make them walk (or run) away and concede that you've won the point but not enough to leave permanent damage.
But that raises another interesting point. It's that hitting someone harder than they hit you proves that you win an argument, ignoring the logic of the situation which might suggest exactlty the opposite. But it's not just two guys in the car park, it's the US, the UK, Russia, etc.