resister

from WordNet (r) 3.0 (2006)

resister
    n 1: someone who systematically obstructs some action that
         others want to take [syn: {obstructionist}, {obstructor},
         {obstructer}, {resister}, {thwarter}]
    2: someone who offers opposition [syn: {adversary},
       {antagonist}, {opponent}, {opposer}, {resister}] [ant:
       {agonist}]

from The Collaborative International Dictionary of English v.0.48

Resister \Re*sist"er\ (-?r), n.
   One who resists.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

24 Moby Thesaurus words for "resister":
      bitter-ender, brawler, defendant, diehard, disputant, dissentient,
      dissident, intransigent, irreconcilable, last-ditcher, litigant,
      naysayer, negativist, noncooperator, objector, obstructionist,
      obstructive, opposer, oppositionist, plaintiff, protester,
      quarreler, scrapper, wrangler

[email protected]