one fell swoop, in

in one fell swoop

All at once, with a single decisive or powerful action. When the economy crashed, thousands lost their jobs, their homes, and their pensions in one fell swoop.
See also: fell, one, swoop
Farlex Dictionary of Idioms.

one fell swoop, in

Also at one fell swoop. All at once, in a single action, as in This law has lifted all the controls on cable TV in one fell swoop. This term was used and probably invented by Shakespeare in Macbeth (4:3), where the playwright likens the murder of Macduff's wife and children to a hawk swooping down on defenseless prey. Although fell here means "cruel" or "ruthless," this meaning has been lost in the current idiom, where it now signifies "sudden."
See also: fell, one
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • at one fell swoop
  • at/in one fell swoop
  • in one fell swoop
  • swoop
  • at a (single) blow
  • at a (single) stroke
  • at a blow
  • in one blow
  • at one stroke
  • at a/one stroke