oppressiveness vs heaviness

oppressiveness and heaviness both are nouns.

Word	Noun	Adjective	Verb	Adverb
oppressiveness	Yes	No	No	No
heaviness	Yes	No	No	No

As nouns, oppressiveness and heaviness are synonyms defined as:

Other synonyms of oppressiveness include burdensomeness, onerousness.

oppressiveness (noun)	heaviness (noun)
unwelcome burdensome difficulty	the property of being comparatively great in weight
a feeling of being oppressed	used of a line or mark
	unwelcome burdensome difficulty
	an oppressive quality that is laborious and solemn and lacks grace or fluency
	persisting sadness