militancy vs aggressiveness

militancy and aggressiveness both are nouns.

Word	Noun	Adjective	Verb	Adverb
militancy	Yes	No	No	No
aggressiveness	Yes	No	No	No

As nouns, aggressiveness is a hypernym of militancy; that is, aggressiveness is a word with a broader meaning than militancy:

militancy (noun)	aggressiveness (noun)
a militant aggressiveness	the quality of being bold and enterprising
	a natural disposition to be hostile
	a feeling of hostility that arouses thoughts of attack