WordNet records no synonym and no antonym for denier. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a unit of measurement for the fineness of silk or nylon or rayon
“with an evening dress one wears 10 denier stockings”
any of various former European coins of different denominations
one who denies
Synonyms, antonyms and the broader and narrower relations for denier come from Princeton University’s WordNet. Full sources and licences.