A colloquial verb meaning to beat/defeat someone, get rid of an enemy/problem, or finish something off (often quickly or forcefully).
相手チームを見事にやっつけた。
We beat the opposing team convincingly.
宿題を早くやっつけて遊びに行こう。
Let's finish the homework quickly and go play.
敵をやっつけるために作戦を立てた。
We made a plan to take down the enemy.