antagonistic vs antagonism

antagonistic is not a noun while antagonism is a noun.

Word	Noun	Adjective	Verb	Adverb
antagonistic	No	Yes	No	No
antagonism	Yes	No	No	No

antagonistic (noun)	antagonism (noun)
	(biochemistry) interference in or inhibition of the physiological action of a chemical substance by another having a similar structure
	an actively expressed feeling of dislike and hostility
	the relation between opposing principles or forces or factors
	a state of deep-seated ill-will

antagonistic (adjective)	antagonism (adjective)
arousing animosity or hostility
used especially of drugs or muscles that counteract or neutralize each other's effect
characterized by antagonism or antipathy
incapable of harmonious association
indicating opposition or resistance