negator

Noun

Meaning

One who, or that which, negates.

(grammar) A word (or other structural element) which causes negation (such as the word not in English).

Source: en.wiktionary.org

denier nullifier antitoxin countermeasure antivenin neutralizer contradictor counterstep disavower

sustainer affirmer confirmer

tronage teragon

negatize negatome negaton negatory negatoscope negatron