combat vs aggression

combat and aggression both are nouns.

Word	Noun	Adjective	Verb	Adverb
combat	Yes	No	Yes	No
aggression	Yes	No	No	No

As nouns, aggression is a hyponym of combat; that is, aggression is a word with a more specific, narrower meaning than combat:

Other hyponyms of combat include belligerency, hostilities, trench warfare.

combat (noun)	aggression (noun)
an engagement fought between two military forces	violent action that is hostile and usually unprovoked
the act of fighting; any contest or struggle	deliberately unfriendly behavior
	the act of initiating hostilities
	a disposition to behave aggressively
	a feeling of hostility that arouses thoughts of attack

combat (verb)	aggression (verb)
battle or contend against in or as if in a battle