ferociousness vs harshness

ferociousness and harshness both are nouns.

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

As nouns, harshness is a hypernym of ferociousness; that is, harshness is a word with a broader meaning than ferociousness:

Other hypernyms of ferociousness include cruelness, cruelty.

ferociousness (noun)	harshness (noun)
the trait of extreme cruelty	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