Payback...

They say that "Payback is a bitch" or that "Payback is a motherf*cker."

My question is:

Is the person that's paying the person or persons who did him wrong a bitch/motherf*cker, or is it the person and/or persons that did him/her wrong the true bitch/motherf*cker?

Needless to say, that this has been on my mind latley as well...