cruelty vs inhumanity

cruelty and inhumanity both are nouns.

Word	Noun	Adjective	Verb	Adverb
cruelty	Yes	No	No	No
inhumanity	Yes	No	No	No

As nouns, inhumanity is a hyponym of cruelty; that is, inhumanity is a word with a more specific, narrower meaning than cruelty:

Other hyponyms of cruelty include impalement, atrocity.

cruelty (noun)	inhumanity (noun)
a cruel act; a deliberate infliction of pain and suffering	an act of atrocious cruelty
the quality of being cruel and causing tension or annoyance	the quality of lacking compassion or consideration for others
feelings of extreme heartlessness