where it counts
Adverb
Meaning
in the most advantageous area or sphere
True, Madeline does not have a lot of book smarts, but she is plenty wise enough where it counts.
in an effective manner
At first the boycott's impact was barely noticeable, but now the protesters are hurting the store where it counts.
(euphemistic) in the testicles
A girl's best weapon — and one that should be used sparingly — is a swift kick where it counts.
Examples
Men are the weak ones, luv. Didn't you know? Oh, you make a lot of noise, but its the women who are strong. Where it counts. In 'ere.