noun
misanthrope, misogynist, misogamist, mocker, satirist, scoffer, pessimist, sarcastic person, caviler, sneerer, flouter, carper, critic, unbeliever, egoist, manhater, skeptic, doubter, questioner, detractor, negativist, nihilist, doubting Thomas*; see also critic 1.
Antonyms optimist, believer*, idealist.