The Collaborative International Dictionary of English v.0.48:

Struggler \Strug"gler\, n.
   One who struggles.
   [1913 Webster]

WordNet (r) 3.0 (2006):

struggler
    n 1: a person who struggles with difficulties or with great
         effort

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "struggler":
   battler, belligerent, belted knight, bickerer, blade, bravo,
   brawler, bully, bullyboy, combatant, competitor, contender,
   contestant, disputant, duelist, enforcer, fencer, feuder, fighter,
   fighting cock, foilsman, gamecock, gladiator, goon, gorilla,
   hatchet man, hood, hoodlum, hooligan, jouster, knight, militant,
   plug-ugly, quarreler, rioter, rival, rough, rowdy, ruffian,
   sabreur, scrapper, scuffler, squabbler, strong arm, strong-arm man,
   strong-armer, swashbuckler, sword, swordplayer, swordsman, thug,
   tilter, tough, tussler, wrangler