luridness vs frightfulness

luridness and frightfulness both are nouns.

Word	Noun	Adjective	Verb	Adverb
luridness	Yes	No	No	No
frightfulness	Yes	No	No	No

As nouns, frightfulness is a hypernym of luridness; that is, frightfulness is a word with a broader meaning than luridness:

luridness (noun)	frightfulness (noun)
the quality of being ghastly	the quality of being frightful
unnatural lack of color in the skin (as from bruising or sickness or emotional distress)
the journalistic use of subject matter that appeals to vulgar tastes