noun
great debt of gratitude; great obligation
Refers to a profound sense of indebtedness for a significant favor or kindness received. Often used in formal or heartfelt expressions of thanks.
彼には大恩があるので、一生かけて恩返ししたい。
I owe him a great debt of gratitude, so I want to repay it over my lifetime.
大恩を忘れてはいけません。
You must not forget a great obligation.