A person can be killed instantly through many different means.
As we know it, to be killed painlessly, is to be killed instantly.
If you instantly destroy a person’s entire brain then they died without pain.
Yet the most effective ways of instantly destroying someone’s entire brain are considered inhumane.
If instantly killing someone by smashing their head with a massive rock, or shooting them in the brain stem is inhumane, then there is no humane way to kill someone at all.
Why did you think killing someone (murder) could ever be humane in the first place?
Because the death penalty exists.
Because people are currently sentenced to execution even in the United States.
To those humans who are sentenced to death, why not choose a method that is instantaneous death, rather than something that can potentially fail.
I’d rather die instantly from a rock or a 12 gauge shell to the head than be injected or electrocuted.
Here is a tip: The world is not the USA…
If you are complaining about something that happens in the USA, say so.