horridness vs unpleasantness

horridness and unpleasantness both are nouns.

Word	Noun	Adjective	Verb	Adverb
horridness	Yes	No	No	No
unpleasantness	Yes	No	No	No

As nouns, unpleasantness is a hypernym of horridness; that is, unpleasantness is a word with a broader meaning than horridness:

horridness (noun)	unpleasantness (noun)
a quality of extreme unpleasantness	the quality of giving displeasure
	the feeling caused by disagreeable stimuli; one pole of a continuum of states of feeling