atrocity vs inhuman treatment

atrocity and inhuman treatment both are nouns.

Word	Noun	Adjective	Verb	Adverb
atrocity	Yes	No	No	No
inhuman treatment	Yes	No	No	No

As nouns, inhuman treatment is a hypernym of atrocity; that is, inhuman treatment is a word with a broader meaning than atrocity:

atrocity: an act of atrocious cruelty
inhuman treatment: a cruel act; a deliberate infliction of pain and suffering

Other hypernyms of atrocity include cruelty.

atrocity (noun)	inhuman treatment (noun)
an act of atrocious cruelty	a cruel act; a deliberate infliction of pain and suffering
the quality of being shockingly cruel and inhumane