hellishness vs nightmarishness

hellishness and nightmarishness both are nouns.

Word	Noun	Adjective	Verb	Adverb
hellishness	Yes	No	No	No
nightmarishness	Yes	No	No	No

As nouns, hellishness and nightmarishness are synonyms defined as:

hellishness and nightmarishness: The property of being extremely bad, miserable, difficult or terrifying; resembling a nightmare.

hellishness (noun)	nightmarishness (noun)
The property of being extremely bad, miserable, difficult or terrifying; resembling a nightmare.	The property of being extremely bad, miserable, difficult or terrifying; resembling a nightmare.