the theory of n and n+1

i have just been taught that the very basic theory behind sparring is the theory of n and n+1. basically if your opponent attacks you n times u attack back by (n+1) times. that's how you score points over your opponent otherwise there will become no point in a match.

and then i realise, this does not only apply to sparring. u receive and you give more back. how often do you do that? when someone is nice to you, u r elated and u return the favour or even much more. but what do you do when the person turns against you? n times. is it now the time to take revenge (n+1) times?

an eye for an eye (or rather an n for an n) makes the whole world blind but what about an eye (or n) for an eye plus a tooth plus an arm plus oh, why not, the whole body (n+1)? You eradicate the whole problem itself, 斩草除根... or do you?