badness vs severity

badness and severity both are nouns.

Word	Noun	Adjective	Verb	Adverb
badness	Yes	No	No	No
severity	Yes	No	No	No

As nouns, badness and severity are synonyms defined as:

badness and severity: used of the degree of something undesirable e.g. pain or weather

Other synonyms of badness include severeness.

badness (noun)	severity (noun)
that which is below standard or expectations as of ethics or decency	excessive sternness
used of the degree of something undesirable e.g. pain or weather	used of the degree of something undesirable e.g. pain or weather
an attribute of mischievous children	something hard to endure
	extreme plainness