The Oxford Thesaurus An A-Z Dictionary of Synonyms - atrocityn.

1) enormity, wickedness, flagitiousness, iniquity, infamy, cruelty, heinousness, horror, evil, inhumanity, barbarity, savagery: The atrocity of the 'Final Solution' was a well-kept secret during the war. 2) evil, outrage, crime, villainy, offence: She could not listen when the prosecutor read a list of the atrocities perpetrated at the camp.