As someone who has had a couple of major surgeries, I don’t understand the problem with the methods used in death penalty cases.
In the hospital, they give you things that are not painful in anyway, the just put you to sleep and for the most part it’s instant, 1-2 seconds and you are gone.
I’m sure they could easily up the dosage and the person would just die and never feel any pain or discomfort.

Pharmaceutical companies will not sell to prisons for executions. I always favored nitrogen asphyxia. Somewhat slow, painless, and there are no hazardous substances (80% of the atmosphere) to deal with. One jamoke who was executed using a face mask made gasping sounds and writhing gestures under the restraints, but he was almost certainly feigning distress to embarass the authorities or in hopes of a temporary repreive. He died.
“The restraints are too tight. They hurt!”
“No worries, we’ll loosen them once you are dead.”
I LIKE FIRING SQUADS. NEVER A SHORTAGE OF BULLETS
It's an unpleaseant duty but our governments need to do it much more often and expeditiously. Our Justice vandalsim is bankrupting us.