malodorousness vs aroma

malodorousness and aroma both are nouns.

Word	Noun	Adjective	Verb	Adverb
malodorousness	Yes	No	No	No
aroma	Yes	No	No	No

As nouns, aroma is a hypernym of malodorousness; that is, aroma is a word with a broader meaning than malodorousness:

Other hypernyms of malodorousness include odor, odour, olfactory property, scent, smell.

malodorousness (noun)	aroma (noun)
the attribute of having a strong offensive smell	any property detected by the olfactory system
	a distinctive odor that is pleasant