cruelness vs harshness

cruelness and harshness both are nouns.

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

As nouns, cruelness and harshness are synonyms defined as:

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

Other synonyms of cruelness include cruelty.

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