expression, godan verb (-su)
take revenge; avenge; settle a score
Used when someone avenges a grudge or regret, often in the pattern 〜の無念を晴らす (avenge someone's regret).
彼は兄の無念を晴らすために戦った。
He fought to avenge his brother's regret.
ついに無念を晴らすことができ
I was finally able to settle the score.