A common subterfuge used by the opponents of the divinely authorized practice of capital punishment is to righteously pontificate about how they could never support the petty practice of personal vengeance.
Such spewings demonstrate an alarming ignorance of God and His word.
Biblically-speaking, justice and revenge are not synonyms. Personal vengeance for a real or perceived slight is never authorized in Scripture. Just punishment of criminal behavior—up to and including the death penalty—has unmistakably been authorized since the post-Flood days of Noah (Genesis 9:6).
On three separate occasions, Moses specifically states that justice—the fair punishment of doing to a criminal what he has done to his innocent victim—is to be the law of the land judicially-speaking: life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burn for burn, wound for wound, stripe for stripe, fracture for fracture, disfigurement for disfigurement (Exodus 21:23-25; Leviticus 24:19-20; Deuteronomy 19:21).
This just punishment was to conclude a fair trial which required the testimony of two or more truthful witnesses and the careful investigation of judges who were authorized to justly punish every false witness (Deuteronomy 19:15-20). This is the protection of the innocent and punishment of the wicked God expects from every civil government.
This is justice, not revenge. Shame on all those who fail to learn the clear differences between them.