忘ぼう恩おん行こう為い

noun

act of ingratitude; ungrateful act

A formal or literary term for an action that shows a lack of gratitude, often implying a betrayal of kindness received.

• 彼かれの忘ぼう恩おん行こう為いには本ほん当とうに失しつ望ぼうした。

  I was truly disappointed by his ungrateful act.