What is another word for "oppositionist"?

Roget's Thesaurus (1911) lists these synonyms for "oppositionist": adversary, adverse, antagonist, assailant, bete, brangler, brawler, competitor, demagogue, disputant, enemy, filibuster, malcontent, obstructionist, obstructive, opponent, opposition, other, party, reactionist, rival, side, the, wrangler.