sad sack

sad sack
    n 1: someone who makes mistakes because of incompetence [syn:
         {bungler}, {blunderer}, {fumbler}, {bumbler}, {stumbler},
         {sad sack}, {botcher}, {butcher}, {fuckup}]
    

75 Moby Thesaurus words for "sad sack":
      Bowery bum, Milquetoast, baby, beachcomber, beggar,
      beggarly fellow, big baby, blighter, budmash, bum, bummer, caitiff,
      chicken, crybaby, derelict, devil, doormat, drifter, drunkard,
      dull tool, good-for-naught, good-for-nothing, gutless wonder,
      hard-luck guy, hardcase, hobo, human wreck, invertebrate,
      jellyfish, lightweight, loser, lowlife, mauvais sujet, mean wretch,
      meek soul, milksop, mollycoddle, mucker, namby-pamby, nebbish,
      no-good, nonentity, pansy, pantywaist, pauvre diable, pilgarlic,
      poor creature, poor devil, poor unfortunate, pushover, sad case,
      schlemiel, schlimazel, sissy, skid-row bum, softling, softy, sop,
      stiff, sundowner, sure loser, swagman, tramp, truant, unfortunate,
      vag, vagabond, vagrant, vaurien, victim, wastrel, weak sister,
      weakling, worthless fellow, wretch