The Collaborative International Dictionary of English v.0.48:

Brutality \Bru*tal"i*ty\, n.; pl. Brutalities. [Cf. F.
   brutalit['e].]
   1. The quality of being brutal; inhumanity; savageness;
      pitilessness.
      [1913 Webster]

   2. An inhuman act.
      [1913 Webster]

            The . . . brutalities exercised in war. --Brougham.
      [1913 Webster]

WordNet (r) 3.0 (2006):

brutality
    n 1: the trait of extreme cruelty [syn: ferociousness,
         brutality, viciousness, savagery]
    2: a brutal barbarous savage act [syn: brutality, barbarity,
       barbarism, savagery]

Moby Thesaurus II by Grady Ward, 1.0:

138 Moby Thesaurus words for "brutality":
   Adam, Gothicism, Neanderthalism, abominableness, acuteness,
   animalism, animality, atrociousness, atrocity, awfulness,
   barbarism, barbarity, barbarousness, baseness, beastliness,
   bestiality, bloodiness, bloodlust, bloodthirst, bloodthirstiness,
   bloody-mindedness, brutalness, brutishness, cannibalism,
   carnal nature, carnal-mindedness, carnality, coarseness,
   contemptibleness, cruelness, cruelty, despicableness,
   destructiveness, detestableness, direness, disgustingness,
   dreadfulness, earthiness, egregiousness, extremity, fallen nature,
   fallen state, ferociousness, ferocity, fiendishness, fierceness,
   filth, flesh, fleshliness, force, foulness, fulsomeness,
   furiousness, grossness, harshness, hatefulness, heinousness,
   horribleness, ill breeding, impetuosity, impoliteness, incivility,
   inclemency, infamousness, inhumaneness, inhumanity, intensity,
   lapsed state, loathsomeness, lousiness, malignity, materialism,
   mercilessness, mindlessness, murderousness, nastiness,
   nefariousness, noisomeness, nonspirituality, notoriousness,
   obnoxiousness, odiousness, offensiveness, outrageousness,
   philistinism, pitilessness, postlapsarian state, rankness,
   repulsiveness, rigor, rottenness, roughness, ruthlessness, sadism,
   sadistic cruelty, sanguineousness, savagery, savagism,
   scandalousness, scurviness, severity, shabbiness, shamefulness,
   sharpness, shoddiness, sordidness, squalidness, squalor,
   swinishness, terribleness, terrorism, the Old Adam, the beast,
   the flesh, the offending Adam, the pits, troglodytism, truculence,
   uncivilizedness, uncleanness, uncouthness, uncultivatedness,
   uncultivation, unculturedness, ungentleness, unrefinement,
   unspirituality, vandalism, vehemence, venom, viciousness, vileness,
   violence, virulence, wanton cruelty, wildness, worthlessness,
   wretchedness