I'll be eternally grateful to you for this.

我将为此永远感激你。

《牛津词典》

She is eternally grateful to her family for their support.

她因家人的支持对他们永存感激之心。

《柯林斯英汉双解大词典》

I am eternally grateful to you for your kindness.

我会永远感激你的善意。

youdao

And for that, Hope, my wife, and my entire family will be eternally grateful to you.

WHITEHOUSE: President Obama Nominates Sally Jewell as Secretary of the Interior | The White House

For that, and for his personal support of me, I am eternally grateful to President Bush.

CNN: Giuliani: 'Thank God that George Bush is our president'

Clearly it was not their time and for that we are eternally grateful.

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