at one fell swoop

The phrase "at one fell swoop" means to do something all at once or in a single act, usually referring to completing a task or achieving a goal in a swift and comprehensive manner. It suggests that something is done quickly, decisively, and without hesitation. The term "fell swoop" refers to a sudden, deadly attack of a bird of prey (such as a falcon or eagle) using a single swooping motion, which is then used metaphorically to describe the swift completion of an action.