The first entry will modify the AppTimeout.
Navigate along the path below :

- HKEY_CURRENT_USER
\Control Panel\Desktop\

In the right pane select the entry :

WaitToKillAppTimeout

(Double click it and set it's value to 1000 (one second))

This entry handles the shutdown instantly prompting :

- HKEY_CURRENT_USER
\Control Panel\Desktop\

Set the vaule of AutoEndTasks to 1.