in one foul swoop

Etymology
Mondegreen variant of in one fell swoop, where "fell" (of a strong and cruel nature; eager and unsparing; grim; fierce; ruthless; savage) is misheard as "foul" (disgusting) or "fowl" (a bird).

Prepositional phrase

 * 1)  (Achieved or completed) with a single action; in a single stroke.