sickening vs offensive

sickening is not a noun while offensive is a noun.

Word	Noun	Adjective	Verb	Adverb
sickening	No	Yes	No	No
offensive	Yes	Yes	No	No

As adjectives, sickening and offensive are synonyms defined as:

Other synonyms of sickening include loathsome, nauseating, nauseous, noisome, queasy, vile.

sickening (noun)	offensive (noun)
	the action of attacking an enemy

sickening (adjective)	offensive (adjective)
causing or able to cause nausea	unpleasant or disgusting especially to the senses
	causing anger or annoyance
	for the purpose of attack rather than defense
	morally offensive
	violating or tending to violate or offend against
	causing or able to cause nausea