The Collaborative International Dictionary of English v.0.48:

Scathe \Scathe\ (sk[=a][th]; 277), Scath \Scath\ (sk[a^]th;
   277), v. t. [imp. & p. p. Scathed (sk[=a][th]d or
   sk[a^]tht); p. pr. & vb. n. Scathing (sk[=a][th]"[i^]ng or
   sk[a^]th"-).] [Icel. ska[eth]a; akin to AS. scea[eth]an,
   sce[eth][eth]an, Dan. skade, Sw. skada, D. & G. schaden, OHG.
   scad[=o]n, Goth. ska[thorn]jan.]
   To do harm to; to injure; to damage; to waste; to destroy.
   [1913 Webster]

         As when heaven's fire
         Hath scathed the forest oaks or mountain pines.
                                                  --Milton.
   [1913 Webster]

         Strokes of calamity that scathe and scorch the soul.
                                                  --W. Irving.
   [1913 Webster]

WordNet (r) 3.0 (2006):

scathing
    adj 1: marked by harshly abusive criticism; "his scathing
           remarks about silly lady novelists"; "her vituperative
           railing" [syn: scathing, vituperative]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "scathing":
   acerb, acerbate, acerbic, acid, acidic, acidulent, acidulous,
   acrid, acrimonious, astringent, biting, bitter, brutal, burning,
   caustic, corroding, corrosive, cutting, damaging, double-edged,
   edged, escharotic, ferocious, fierce, harmful, harsh, incisive,
   keen, mordacious, mordant, nasty, penetrating, piercing, poignant,
   rigorous, rough, salty, savage, scorching, searing, severe, sharp,
   stabbing, stern, stinging, strident, stringent, tart, trenchant,
   vehement, violent, virulent, vitriolic, withering