Shutdown process in Windows 8 needs a multiple screen process because the power button is hidden in the setting menu, but we can pin a shutdown button on our task bar to facilitate ourselves an one-click shutdown.
Here is how-
Create a shortcut (right mouse click, navigate to NEW tab then click on the shortcut).Now enter "Shutdown /s /t O" (remove the quotes) in the box of location. Name it as "Shutdown."
|one click shutdown button in Windows 8 screenshot 1|
|one click shutdown button in Windows 8 screenshot 3|