One thing that is always true: Revenge belongs to God. If nations do not do what God set them up to do, and the sins of those nations continue to offend God sufficiently, then those nations will collapse, and God will raise up another authority in its place.
See the examples of Sodomites, Gomorrhites, Egyptians, Caananites, Amalekites, Philistines, Assyrians, Babylonians, Israelites, Judaeans, Greeks, Romans, and on to the modern nations we know, which even now are beginning to show signs of crumbling. Because of sin and the dereliction of duty on the part of their authorities, God set his face against these peoples and they were destroyed, their power was taken from them, their people made into a disgrace. And God did not make it that these nations fell peacefully, but by the sword, by pestilence, some even by fire were made into their ruin.
Therefore it is essential that nations continue to rightly observe their duties, and within their competency exercise the power God granted to them, so that with respect for persons and for God they might continue to exist for the glory of God by whose mercy they are permitted even to exist. The death penalty is not itself always evil, we know this because we ought to fear the Lord’s just penalty, lest he should determine that our own countries are deserving of it. It is a fearful thing to fall into the hands of the Living God.
For the same reason we should be extremely slow to take the life of anyone unjustly, because that is one of the gravest sins, which cries out to heaven for vengeance, and more swiftly than all of them will it incur the wrath of the Almighty.