harshness vs cruelness

harshness and cruelness both are nouns.

Word	Noun	Adjective	Verb	Adverb
harshness	Yes	No	No	No
cruelness	Yes	No	No	No

As nouns, harshness and cruelness are synonyms defined as:

harshness and cruelness: the quality of being cruel and causing tension or annoyance

Other synonyms of harshness include cruelty.

harshness (noun)	cruelness (noun)
the quality of being harsh or rough or grating to the senses	the quality of being cruel and causing tension or annoyance
excessive sternness
the roughness of a substance that causes abrasions
the quality of being cruel and causing tension or annoyance