rue the day

Verb

idiomatic

(idiomatic) To seriously regret one's actions.

Japanese Meaning

深く後悔する / 自分の行いを激しく悔いる

If you betray me, you will rue the day you ever crossed me.

もし私を裏切れば、私に逆らったことを深く後悔することになるだろう。

Sense（1）

(idiomatic) To seriously regret one's actions.

I: I think there may be something living in there. I think there may be something alive.

Withnail: What d'you mean? A rat?

I: It's possible. It's possible.

Withnail: Then the fucker will rue the day!

rues the day

（ present singular third-person ）

ruing the day

（ participle present ）

rued the day

（ participle past ）

rued the day

（ past ）