Here's a couple I could find from the OT (there are none in the NT). It is by no means a comprehensive list, just whatever references I could find in my spare time. Keep in mind that God dealt severely with the enemies of Israel, and even the nation of Israel itself when it was in disobedience, for one reason: the preservation of the nation. God's will was to preserve the nation of Israel, which He had set apart or made holy from the rest of the world, because it was by Israel that a Redeemer, the Messiah and Son of God, would come into the world to die for the sins of both Jew and Gentile. That is the reason God implemented the Law and Prophets, in order that the lineage leading to Christ (see the gospels for lineage through Mary and through Joseph) would be intact. Such strict dealings were necessary, and God was just in it all. God alone has the right to take away and to give life because He is the one that gave it, gives it, and preserves it. We see that the nation of Israel was indeed preserved by God's protection (even though they had nearly destroyed themselves many times because of their disobedience), like no other nation has been preserved over thousands of years, and that indeed the Messiah did come into the world 2,000 or so years ago to die on a cross for our sins. That is why there is no record of God commanding the nation to kill anyone in the NT - it was no longer necessary for the bringing of the Messiah. God is still protecting Israel from absolute destruction, though, and even though the nation as a whole has turned away from Him and have rejected His Son, He will turn their hearts to Him just before the return of the King, Jesus Christ.
Exodus 19:12-13 - God commands that no one should approach His presence on the mountain or even the base of the mountain, under
penalty of death.
Exodus 22:18 - "Do not allow a witch to live".
Numbers 31 - God tells the nation of Israel to take vengeance on
the Midianites. The Midianites were a nomadic people, distantly related
to the Israelites. Earlier in the book of Numbers, chapter 22, we see that the Midianites had made themselves
enemies of Israel by joining forces with the Moabites in hiring the false prophet/magician Balaam to curse the nation of Israel.
Deuteronomy 13 - God institutes the penalty of death for false prophets and anyone trying to apostasize (lead the people way from) God.
Joshua 7 - God told the people via Joshua not to take anything "accursed" thing of Jericho, a Canaanite city (the Canaanites were a wicked people who worshipped false gods). Achan disobeys by pocketing, by his own admission, "the spoils a beautiful Babylonian garment, two hundred shekels of silver, and a wedge of gold weighing fifty shekels". God commands that he, his family, and everything he had to be burned with fire.
Joshua 8 - God tells Joshua to make war against Ai, another Canaanite stronghold.
Judges 20 - In the previous chapter, there is recorded the really awful rape and murder of a woman, and her cold and callous husband that rallies the nation to war by cutting up her body and sending the pieces to the tribes of the nation (that chapter is one that really shows how wicked mankind can be).In chapter 20 the tribes of Israel ask for permission to fight against the tribe of Benjamin (one of the 12) because among them were the perpetrators of the crime and the general state of the city of Gibeah was one of wickedness.
1 Samuel 15 - God commands Saul to completely destroy Amalek, and not leave anyone alive. Saul lets Agag, the king, live. Saul,
for his disobedience, would be taken out as king by God, and replaced by a "man after God's own heart", David. Samuel, a prophet of God, does what Saul should have done and kills Agag. The descendents of Agag, the Agagites, continue to harrass the nation of Israel for generations, and they are not completley destroyed until the book of Esther, when Haman the Agagite is hanged on his own gallows after his attempt to have all the Jews killed fails.