iOS - Cancel Update All in App Store
Currently, there is no one button way to cancel or stop all the updates started by pressing the "Update All" button, maybe in a future release of iOS we can have a Cancel All or Pause all. Submit your feeback to Apple, here.

The current solution is to manually stop updating each app that was started updating:


First turn off your data if you are concerned with burning through metered data. Switch your iOS device into Airplane mode via Control Center
Open the App Store app, switch to the "Updates" tab.
Then tap on the download progress circle for each app that is waiting to update.