You are nuts if you think George III couldnt have your life if he wanted it.
The Bloody law meant England had over 200 death offenses into the 1800s. They could even execute you for spending a month with a gypsey. Minor poaching (pretty neat when the king or his buds owns all the land),
Yes, Mopnarchs could kill you. And when they couldnt, they could lock you up in conditions that would kill you just as handily. Europe is good at supressing dissent and murder.
They only nominally behave now because of the USA and WWII. Enforced peace,,,,
However, regarding the death penalty, George III did use his influence to prevent a madwoman who had tried to assassinate him from suffering the death penalty, and she was confined to an asylum instead. Rather enlightened for the time considering that, as you have also pointed out, far less serious crimes were eligable to a sentence of death by hanging...