The worst thing is when you call friends and they've gone out.

最糟糕的是，你给朋友们打电话时他们却出去了。

《柯林斯英汉双解大词典》

In fact, the worst thing is not to do anything.

事实上，最糟糕的事情是不做任何事。

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And the worst thing is, they're not even fun.

最糟糕的一点是，这些事情甚至一点都不娱乐。

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And,he says the worst thing is that he does not even know if the investigation is active.

VOA: standard.2009.08.04

And the worst thing is the paperwork, you know.

最坏的事是书面作业。

在公园相遇的老师 - SpeakingMax英语口语达人

That's sort of what that's like, but the really important thing is what's the worst thing that can happen.

这和我们说的有点相像，但是真正重要的事情是,可能发生的最坏的事情是什么。

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The worst thing is when you are teasing or nagging or judging.

WSJ: How to Help an Overweight Partner Lose Weight

The worst thing is we have only one more game left.

BBC: Cricket World Cup: Rusty Australia reach last eight

You know the worst thing is standing on a station not knowing whether a train's going to come in and now knowing how long it's going to take you.

BBC: George Muir and Stuart Francis