Not according to God.
God is the One who instituted the death penalty for murder.
Genesis 9:5-6 And for your lifeblood I will require a reckoning: from every beast I will require it and from man. From his fellow man I will require a reckoning for the life of man. “Whoever sheds the blood of man, by man shall his blood be shed, for God made man in his own image.
Capital punishment is not murder.
I have never had an issue with people exacting justice.
Family member is murdered?
Put the POS cretin in a room, slice their Achilles and put out their eyes. Give the victim’s families machetes and axes and close the door for a day or two.
Let the people have at it, not the government
The instruction to Noah’s family (all of us) and the ideas of a Magistrate to act on behalf of the people works just fine in a moral society. Plato’s republic and the enlightened, benevolent Kings etc . . .
I have a problem with a corrupt government choosing, convicting and then killing people. Adolf did it. Mao did it. Uncle Joe did it. Bull Connor and other Dems in ole’ Dixie did it. FDR wanted to do it. Obama wants to do it.
Take the plunge. Revenge is a personal thing. We can all face our Creator with a clean conscience if we were protecting innocents. A government that kills people is a kind of hell waiting to take over.