going through thick and thin to attain one's objective; enduring unspeakable hardships for the sake of vengeance
臥薪嘗胆の末に宿敵を打ち破った。
After enduring great hardships, he defeated his nemesis.
臥薪嘗胆の精神で苦しい日々を耐えた。
With a spirit of perseverance, I endured the difficult days.
彼は臥薪嘗胆し十年後に復讐を遂げた。
He endured hardships and achieved his revenge after ten years.