To experience a hard immediate shutdown , try the following steps ( I don't know whether this is a proper shutdown or not , so don't use it often )
(1) Open task manager (Ctr+Alt+Del),
(2) Select shut down tab and click on Turn Off while pressing CTRL key . Your Windows will rapidly shut down.
I think this feature kills all the processes and hence your system shutdowns instantly . You know exactly what it is , then drop in a comment .