in one fell swoop
in one fell swoop or at one fell swoop {adv. phr.}
1. {literary}
In one attack or accident; in one bad blow.
The millionaire lost his money and his friends at one fell swoop.
2. At one time; at the same time.
Three cars drove into the driveway, and Mrs. Crane's dinner guests all arrived at one fell swoop.
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Source: A Dictionary of American Idioms