a bad/rotten apple

a rotten apple

A person whose own words or actions negatively impacts an entire group of people. Taken from the proverb "a rotten apple spoils the bunch." Before you accuse the entire department of wrongdoing, you should try to find the rotten apple that initially caused the problem. A: "Jeremy is such a brat. He won't listen to a word I say, and he gets the other kids all riled up too!" B: "Sounds like a rotten apple to me." It used to be considered the top research facility in the region, but after one of its researchers was discovered to have plagiarized a number of his papers, the whole department's reputation has been dragged through the mud. A rotten apple really does spoil the bunch.
See also: apple, rotten
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.

a bad apple

or

a rotten apple

COMMON If someone is a bad apple or a rotten apple, they are very dishonest or unpleasant, and they have a bad influence on the people around them. It's an opportunity for them to make clear that they are not going to tolerate a bad apple in the United States Senate. In any profession, there's always the rotten apple, isn't there. Note: If a rotten apple is stored with good apples, it causes the good ones to rot.
See also: apple, bad
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

a rotten (or bad) apple

a bad person in a group, typically one whose behaviour is likely to have a corrupting influence on the rest. informal
See also: apple, rotten
Farlex Partner Idioms Dictionary © Farlex 2017

a bad/rotten ˈapple

one bad person who has a bad effect on others in a group: In response to the allegations of mass corruption within the team, a former player said today, ‘There may be the odd rotten apple in the pack, but the majority are clean and honest.’
See also: apple, bad, rotten
Farlex Partner Idioms Dictionary © Farlex 2017
See also: