rotten apple —(coll.) a single bad person in a group (also: bad apple):
- Today, the company, a shadow of its former self, is the rotten apple of the highly competitive supermarket sector.
rotten egg —(coll.) a bad or despised individual (also: bad egg):
- But even if he was a rotten egg, what could he actually do? Does he stonewall any important cases before they reach the Supreme Court?