badness vs seriousness

badness and seriousness both are nouns.

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

As nouns, seriousness is a hyponym of badness; that is, seriousness is a word with a more specific, narrower meaning than badness:

Other hyponyms of badness include foulness, raininess, distressfulness.

badness (noun)	seriousness (noun)
that which is below standard or expectations as of ethics or decency	the trait of being serious
used of the degree of something undesirable e.g. pain or weather	the quality of arousing fear or distress
an attribute of mischievous children	an earnest and sincere feeling