一いっ生しょうの不ふ覚かく

expression, noun

greatest mistake of one's life

A dramatic set phrase used when someone makes an irreparable, deeply regrettable blunder that will haunt them forever. Often used in self-reproach or to describe a catastrophic error.

• あんな簡かん単たんなミスをするなんて、一いっ生しょうの不ふ覚かくだ。

  Making such a simple mistake is the greatest blunder of my life.

• 彼かれはその決けつ断だんを一いっ生しょうの不ふ覚かくだったと後こう悔かいしている。

  He regrets that decision as the worst mistake of his life.