I regret to have made your acquaintance so late.

识荆恨晚。

《新英汉大辞典》

I went so far as to regret the loss of the animal.

我甚至后悔失去了它。

youdao

I just finished Neal Roese's book, If Only: How to Turn regret Into Opportunity, and so I've been thinking a lot about the role of regret.

我刚刚读完了Neal Roese的书，如何将后悔变成机会，关于后悔在生活中扮演的角色我思考了很多。

youdao

So I regret to report I could not have said it better myself.

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Now, you must believe me, gentlemen, many years have passed, and I regret having eaten so little of it.

NEWYORKER: Bear Meat

It tastes so good that I will regret not keeping more.

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