detractor
Definitions
A person who disparages someone or something.
One who seeks to diminish the worth or importance of a person or idea.
Examples
Despite the project's success, a vocal detractor continued to criticize the team's methodology.
The politician ignored every detractor and focused on implementing his new policy.
Even the harshest detractor had to admit that the performance was truly impressive.
Synonyms
critic cynic naysayer belittler disparager faultfinder opponent