counterworker

noun2

1. •
   (rare) One who works at a counter.

   • When a desired part is not in stock, the counterworker must be able to suggest a different, though interchangeable, part. — 1983
2. •
   (rare) One who works against something; a saboteur.

   • In the midst of this serene sunshine there was a malignant counterworker... — 1880