Definition
Until the very end of an action or process; until something is completely finished or accomplished.
到底
He believed his conviction was right, so he would fight to the last.
他相信自己的信念是正確的，所以他會戰鬥到底。
Even though time was short, the team worked to complete the project to the last.
儘管時間所剩無幾，團隊還是努力將專案完成到底。
Their dance performance was spectacular, maintaining a high standard to the last.
他們的舞蹈表演非常精彩，一直保持高水準直到最後。
Until the end of one's life; throughout one’s life, up to the moment of death.
直到死亡
She was a loving mother to the last.
她直到生命的最後一刻都是一位充滿愛心的母親。
He was a loyal friend to the last.
他直到生命的最後一刻都是一位忠實的朋友。
He was a steadfast leader to the last.
他直到生命的最後一刻都是一位堅定的領導者。