A bad reaction is in a minimum of cases Versi, If I had a choice I'd still choose lethal injection of this barbarity:

"Painlessness

If the headsman's axe or sword was sharp and his aim was true, decapitation was quick and was presumed to be a relatively painless form of death. If the instrument was blunt or the executioner clumsy, however, multiple strokes might be required to sever the head. The person to be executed was therefore advised to give a gold coin to the headsman to ensure that he did his job with care. Robert Devereux, 2nd Earl of Essex, and Mary, Queen of Scots, required three strikes at their respective executions. Margaret Pole, 8th Countess of Salisbury, required ten strokes before the fatal blow.[citation needed]
The Beheading of Cosmas and Damian, by Fra Angelico

To ensure that the blow would be fatal, executioners' swords usually were blade-heavy two-handed swords. Likewise, if an axe was used, it almost invariably would be wielded with both hands. In England a special form of axe was used for beheadings, with the blade's edge extending downwards from the tip of the shaft.[citation needed]

Finland's official beheading axe resides today at the Museum of Crime in Helsinki. It is a broad-bladed two-handed axe. It was last used when murderer Toivo Koljonen was executed in 1826. All subsequent Finnish executions were made by firing squad. Capital punishment is no longer practiced in Finland."

Sorry I couldn't find any links about the current painlessness of beheading but this is the 21st century and very few places still behead.

literal people are scary, man, literal people scare me
out there trying to rid the world of its poetry while getting it wrong fundamentally down at the church of "look,it sez right here, see!" Ani Difranco