violence vs aggression

violence and aggression both are nouns.

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

As nouns, aggression is a hypernym of violence; that is, aggression is a word with a broader meaning than violence:

Other hypernyms of violence include hostility.

violence (noun)	aggression (noun)
an act of aggression (as one against a person who resists)	violent action that is hostile and usually unprovoked
the property of being wild or turbulent	deliberately unfriendly behavior
a turbulent state resulting in injuries and destruction etc.	the act of initiating hostilities
	a disposition to behave aggressively
	a feeling of hostility that arouses thoughts of attack