naysayer
Definitions
A person who habitually expresses negative views or opposes new ideas.
Someone who habitually doubts or denies the truth, efficacy, or feasibility of something.
Examples
Despite being a constant naysayer, he eventually admitted that the new project was a success.
Don't let any naysayer discourage you from pursuing your ambitious career goals.
The proposal faced opposition from every naysayer in the room, but the team pushed forward regardless.
Synonyms
cynic pessimist critic detractor skeptic killjoy faultfinder
Antonyms
optimist advocate supporter believer enthusiast proponent cheerleader