Which execution methods are the worst and which ones are the least painful?

I'm talking about execution methods through the whole human history and not only these used today. Here's my opinions at the subject.

Least painful execution methods.
In my opinion there's no humane execution and I'm against death penalty. But some executions are just lesser painful than others I guess. Here's my guesses.
- Shooting (If they hit correct)
- Lethal injection (If done correctly and with the right ingredients)
- Beheading (But it's a bit messy though)
- Long drop hanging (Your neck would break)

Worst execution methods.
- Flaying
- Impalement
- Boiling/burning someone alive
- Breaking Wheel
- Colombian slips
- Blood eagle
- Crucifixion
- Hanged, drawn & quartet
- Rat torture
- Bamboo torture
- Scaphism

Which execution methods are the worst and which ones are the least painful?

#Execution #WorstExeMethod
Updates
+1 y
I forgot to mention the snake method. The convicted are bound to a chair and the mouth is forced open. Then the executioner puts a alive snake down his throat and the convicted would get choked to death.
Which execution methods are the worst and which ones are the least painful?
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