An angel of the Lord went forth and smote an Assyrian camp (2 Kings 19:20-34)—“behold, they were all dead corpses.” The Assyrian army was annihilated.
A “Destroyer” was sent to slay all the firstborn of heathen Egypt due to their enslavement of God’s people and steadfast refusal to release them, despite repeated warnings accompanied by awesome miraculous plagues.
King David narrowly missed angelic execution. A destroying angel was sent, but later withheld, to punish David for his disobedience and vanity in taking a census of the people.
In Caesarea, the idolatrous King Herod Agrippa I was executed by an angel that smote him, and the king was “eaten of worms” (12:19-23).
What is The Destroyer? Answer
Satan (the Devil) has the “power of death” (Hebrews 2:14), not as lord, but as an executioner—held in check by God. (See: Ryan E. Stokes, “Satan, YHWH's Executioner,” Journal of Biblical Literature, Vol. 133, No. 2 (Summer 2014), pp. 251-270.)
God sometimes used the Israelites as executioners of idolatrous evil people(s).
Evil people used by God
God also used evil people(s) as executioners of disobedient and idolatrous Israelites.
Witnesses were designated by Hebrew law as the first to execute the judge’s sentence on the condemned (Deuteronomy 13:9; 17:7; 1 Kings 21:13; Matthew 27:1; Acts 7:57-58)
Stoning by the people
Certain Israelites offenders were prescribed execution by stoning by their peers.
Execution by sword, strangling or fire
Other modes of capital punishment according to the Mosaic law were by the sword (Exodus 21), strangling, and fire (Lev. 20).
Haman, the Amalekite and vizier, was executed, by order of the Persian King Ahasuerus, on a gallows for attempting to exterminate the Jews (Esther 3-7).
These bodyguards could also be used as executioners by their king.
When Herodias’ daughter Salome asked King Herod Antipas for the head of John the Baptist on a platter…
“Immediately the king sent an executioner and commanded his head to be brought. And he went and beheaded him in prison” (Mark 6:27)
In the above verse, instead of the Greek word for executioner, Mark uses a Latin word, speculator, which literally means “a scout,” “a spy,” and at length came to denote one of the armed bodyguard of the emperor. Herod Antipas, in imitation of the emperor, had in attendance on him a company of speculatores. They were sometimes employed as executioners, but this was a mere accident of their office.