In a boy's / man's case, then nuts / balls, head or asshole.

In a girl's, / woman's case, that can be her titties / boobies, head, or asshole.
Boy 2: Girl 1 kicked Boy 1 where it hurts! What a bitch-ass mothafucka!
Girl 1: I kicked Boy 1 where it hurts because he kicked me where it hurts.
Boy 2: Oh ok.
by RetroGalacticGamer April 5, 2020
To hurt someone where you know it'll be painful the most
Ima hit him where it hurts, his family.
by John Williamson September 12, 2017
Response given to someone who is annoyed at all the extra time they've been putting in at work even though they are being compensated for it.
Rob was whining about putting in a 60 hour work week so I told him to "rub your paycheck where it hurts"
by Calihog July 27, 2009