noun
great benefactor; person to whom one is greatly indebted
Refers to someone who has provided significant help or support, often in a life-changing way. Carries a strong sense of gratitude.
彼は私の大恩人です。
He is my great benefactor.
大恩人に感謝の手紙を書いた。
I wrote a letter of thanks to the person to whom I am greatly indebted.