It would seem that the last batch of updates from Microsoft around the 12th-14th May 2015 have been causing quite a few PC’s to hang stopping at Update 3 of 3.
This so far looks like it is only affecting Windows 7 Pro X64 based PC’s
As with most IT Professionals, we would never suggest performing a Hard shut-down to your PC, unless there really is no other option, however it does look like in this case this is the only way to fix this particular ‘Stuck Update‘ issue.
If your Windows Update stuck: 
Option 1)
Press CTRL + ALT +DEL
This seems to be working for 50% of users encountering this issue, if it does not work then proceed to option 2.
Option 2)
Step 1) Hold down the power button on your PC for 10+ seconds,
Step 2) Restart PC by repressing the power button
Step 3) If confronted with a windows error ‘Your PC did not shut down normally’ screen, select “Start Windows Normally”
Out of the 7 PC’s we have now done this to, all in different environments, we are yet to see any errors or corruptions caused by this. We are continuing to look into which update specifically caused this and why, and so check back later to keep yourself updated.
For further reading see this Reddit thread.