piranha vs aggressor

piranha and aggressor both are nouns.

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

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

Other hypernyms of piranha include assailant, assaulter, attacker.

piranha (noun)	aggressor (noun)
small voraciously carnivorous freshwater fishes of South America that attack and destroy living animals	someone who attacks
someone who attacks in search of booty	a confident assertive person who acts as instigator