that's done it!

That's done it! and That's torn it! ( = Something bad has been done or has happened right now!) -- ну все! Все пропало! Хана! Писец! ...

an exclamation of frustration when something is ruined or is going wrong and as a result you may be in trouble
(переводим контекстуально)

Example: We've missed our train. That's done it! Now we'll never get there in time for the match.

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That's done it! is also an exclamation when something is completed