How do I turn off my Verizon HTC One M8 do I can do a factory reset after a failed Lollipop update?

[AC Question]

verizon htc one m8 lollipop update fail

Message "Unfortunately Verizon Login has stopped" loops. Cannot turn the phone off. I can see a greyed out Power Off button but the error message never gives up control. How can I turn the machine off so I can do a factory reset??