Synonyms and related words :
adversary, antagonist, anti, bitter-ender, brawler, con, defendant, diehard, disputant, dissentient, dissident, intransigent, irreconcilable, last-ditcher, litigant, match, naysayer, negativist, noncooperator, objector, obstructionist, obstructive, oppositionist, oppugnant, plaintiff, protester, quarreler, resister, scrapper, wrangler