atrocity

An extremely cruel act; a horrid act of injustice.

to carry out / commit / perpetrate an atrocity

The regime is guilty of mass atrocities including forced displacement and the use of chemical weapons.

The quality or state of being atrocious; enormous wickedness; extreme criminality or cruelty.

1553, John Bradford, letter, in Miles Coverdale (ed.), Certain Most Godly, Fruitful, and Comfortable letters, London: John Day, 1564, pp. 481-482, Thys wil I muse on, & way with my self, [tha]t I may dulye knowe, both in me and in al other things, the atrocitie and bitternesse of synne which dwelleth in me, & so may the more hartely geue ouer my self wholy to [th]e lord Christ my Sauiour,

What character is so detestable as that of one who takes pleasure to sow dissention among friends, and to turn their most tender love into mortal hatred? Yet wherein does the atrocity of this so much abhorred injury consist? […] It is in depriving them of that friendship itself, in robbing them of each others affections […]

An object considered to be extremely unattractive or undesirable.

[S]ome of the printers were good singers and others good performers on the guitar and on that atrocity the accordeon—[…]

The Pools had given them a “hanging lamp,” coveted by the farmer’s wife; a hideous atrocity in yellow, with pink roses on its shade and prisms dangling and tinkling all around the edge.