Synonyms for Antagonistic:

adj.

aggressive (adjective)
confrontational.
all (adjective)
antipathetic, counter, antipathetical.
at variance (adjective)
opposing.
conflicting (adjective)
differing, cacophonous, dissonant, hostile, loath, antipathetic, bickering, discordant, brawling, dissenting, tense, warring, conflicting, clashing, disharmonious, clamoring, rowing, rioting, contentious, raucous, colliding, dissident, feuding, harsh, Squabbling.
contentious (adjective)
argumentive, confrontational, contrary, controversial, resistant, conflicting, dissenting, protesting, oppositional, quarrelsome, contentious, dissident.
discordant (adjective)
unmusical, tuneless, discordant, jarring, cacophonous, differing, unmelodious, unharmonious, contentious, dissonant, hostile, fricative, discord, disharmonious, conflicting, quarrelsome, inharmonious.
malevolent (adjective)
ill-natured, treacherous, malicious, corrosive, churlish, baneful, catty, spiteful, hateful, sinister, Black-hearted, virulent, baleful, evil, foul, sullen, malevolent, venomous, vicious, malignant, nasty, wicked, hurtful, mean, hostile, rancorous, bitter, vindictive, perfidious.
opposed (adjective)
antipathetic.
opposing (adjective)
inimical, oppositional, hostile, adversarial, unfriendly.
resentful (adjective)
irritated, offended, embittered, stung, malevolent, sore, Huffed, splenetic, spiteful, discontent, Spleenful, bitter, vexed, resentful, acerbic, Piqued, envious, galled, infuriated, miffed, vindictive, hurt.

n.

rebellious, (dead) set against something, Against. opposed, adversarial, adverse, support, opposing. antagonistic (noun)
negative, counter, hostile, incompatible, antagonizing, antipathetic, alienating, antipathetical, antagonising.
unfriendly (noun)
distant, aloof, stony, unpleasant, cold, icy.

v.

opposing (verb)
inimical, unfriendly.

Other synonyms:

rebellious, adversarial. opposed, opposing. Against. hostile
adverse, unfriendly.
unfriendly
unpleasant, cold, stony, icy.
Other relevant words:
antagonising, opposing, adversarial, inimical, rebellious, alienating, unpleasant, unfriendly, negative, Against, adverse, opposed, antipathetical, antagonizing, incompatible, counter.

Usage examples for antagonistic

  1. Why should you be friendly to me when I represent all that is antagonistic to you? – The Puppet Crown by Harold MacGrath
  2. Now whereas in Italy, its original home, this took a warp definitely antagonistic to Christian faith and Christian ethics, in Northern Europe the new classical learning was harmonized with Christianity, and classical learning was applied to the interpretation of the Bible. – The Unity of Civilization by Various
  3. Kara first made a strong appeal to you when you were lonely and antagonistic toward your new life in a small New England town. – The Girl Scouts in Beechwood Forest by Margaret Vandercook