inhuman treatment vs ill-usage

inhuman treatment and ill-usage both are nouns.

Word	Noun	Adjective	Verb	Adverb
inhuman treatment	Yes	No	No	No
ill-usage	Yes	No	No	No

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

inhuman treatment: a cruel act; a deliberate infliction of pain and suffering
ill-usage: cruel or inhumane treatment

Other hypernyms of inhuman treatment include abuse, ill-treatment, maltreatment.

inhuman treatment (noun)	ill-usage (noun)
a cruel act; a deliberate infliction of pain and suffering	cruel or inhumane treatment