contradictor
/ˌkɑntrəˈdɪktər/
noun
- A person who says the opposite of what someone else has said; someone who disagrees or denies something.
- In the debate, each contradictor tried to prove the other wrong.
- The teacher asked the contradictor to explain why he disagreed with the author's main point.
- He was known as a constant contradictor, always finding fault with every suggestion.