Binyamin is compared to a wolf by Yaakov in the brachos in parshas Vayechi because he just like in a wolf he will attack in the morning and save his booty to divide in the evening. Same is with Binyamin, he had Shaul who killed out most of Amalek and then Mordechai much later who also killed out Amalek.
That is what I learned in 4th grade.