attacker vs aggressor

attacker and aggressor both are nouns.

Word	Noun	Adjective	Verb	Adverb
attacker	Yes	No	No	No
aggressor	Yes	No	No	No

As nouns, attacker and aggressor are synonyms defined as:

Other synonyms of attacker include assailant, assaulter.

attacker (noun)	aggressor (noun)
someone who attacks	someone who attacks
	a confident assertive person who acts as instigator