This is a common misconception about Insta-Kill

[@ThaRoach]

Why was the player on Call of Duty Zombies always getting the "Insta-Kill" power-up?
Because it's the only time they can finally say they're getting through life "one-shot at a time!"

[@hazzardgaming405]

does anything else knock zombies down like that temporarily I wonder?

[@khalifornyia8501]

Maybe one of the buildable shields or melee weapons on high rounds…

[@Esakhbs]

Well it’s called insta-kill for a reason