英語：お悔み

I would like to extend my deepest condolences on the sudden death of your aunt. あなたのおばの急死に心からお悔やみを申し上げます。
※congratulationsと同じように、condolencesは複数形。

It must be very difficult for you. I can't imagine what you are going through. If there's anything I can do for you, please let me know.

I am very sorry to learn the passing away of Mr. ... We all miss him.