ambusher vs aggressor

ambusher and aggressor both are nouns.

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

As nouns, aggressor is a hypernym of ambusher; that is, aggressor is a word with a broader meaning than ambusher:

ambusher: an attacker who waits in a concealed position to launch a surprise attack
aggressor: someone who attacks

Other hypernyms of ambusher include assailant, assaulter, attacker.

ambusher (noun)	aggressor (noun)
an attacker who waits in a concealed position to launch a surprise attack	someone who attacks
	a confident assertive person who acts as instigator