The first display of the wrath of God against a mass of sinners occurred when he caused a great flood to cover the entire earth (Genesis 6:7, 7). Except for those inside Noah’s Ark, the entire human race is killed. This cataclysmic event, where approximately ONE BILLION people received the death penalty, was brought miraculously by God because “. . . every imagination of the thoughts of his (man's) heart was only evil continually" (Genesis 6:5, HBFV).
The second great mass event that revealed the Lord's wrath against sin happened when Sodom and Gomorrah were destroyed. These cities were located in a place that was like the Garden of Eden (Genesis 13:10). They were "great metropolises, with large populations and complex cultures" (Biblical Basis for Modern Science, chapter 10). The destruction of these two huge population centers, by heavenly fire and brimstone (Genesis 19:13, 24 - 25), is a testament that God and his wrath can come upon anyone.
In Egypt, after nine plagues have no effect in causing Pharaoh to release his Israelite slaves, the wrath of God produces one final miracle that finally gets him to act. A death angel is sent, at night, to kill all the firstborn humans (mostly Egyptians) who do not have lamb's blood around their doorposts (Exodus 12:7, 21 - 23, 29). A short time after this mass killing, the entire Egyptian army is miraculously drowned in the Red Sea as they are pursuing the fleeing children of Israel (Exodus 14:27 - 28).
The price of whining
Many Israelites, as they travel to the Promised Land, are killed when fire from God consumes some who are complaining (Numbers 11:1). A short time later, the Israelites' whining about manna, miraculously provided each day (except Sabbath), is answered not only by quail sent to them to eat but also a plague that kills many (Numbers 11:31 - 35).
Ten of the twelve spies Moses sent to scout out the Promised Land are struck dead soon after their return (Numbers 14:36 - 37). They are the recipients of God's wrath for their report that it would be near impossible (from a human perspective) for the Israelites to take control of Canaan.
Korah, Dathan, Abiram and 250 of their followers directly challenge the responsibilities God has given to Moses and Aaron (Numbers 16:1 - 3). The Lord's wrath is kindled against this rebellion and he kills the three men (and their families) through the earth opening up (verses 28 - 33). The day after this punishment, many Israelites blame the two leaders for what happened. Their protests are answered with a rapidly spreading plague that ultimately takes the life of 14,700 (verses 41 - 49).
Continuing their whiny ways, the Israelites complain yet again about the manna they receive and their lack of water. The response from God is a swarm of deadly snakes that kills many (Numbers 21:6). After camping in Shittim for a period of time the people begin to intermarry with the pagan Moabites. This leads them to indulge in immorality and idolatry, which arouses the Eternal's wrath. As punishment he sends a plague that kills 24,000 (Numbers 25:9).
Mass punishment in Canaan
Many men of Beth-shemesh, including several who were leaders in the community, are killed by God when the Ark of the Covenant is pried open and its contents viewed (1Samuel 6:18 - 20). King David foolishly takes a census of all his fighting men and incurs the Eternal's wrath. He and the nation are punished by a death angels executing 70,000 Israelites (2Samuel 24:10, 15).
The angel of the Lord, sent by God, kills (in a single night) the ENTIRETY of Assyrian King Sennacherib's army that surrounds Jerusalem. In the morning, instead of seeing 185,000 troops gathered to attack, those in the city gaze upon a vast field of corpses (2Kings 19:32 - 35).
The wrath to come
The "Day of the Lord" refers to a series of events that occur during the final part of the Great Tribulation. This period is the time when God and his wrath are manifested against those who have adopted the mark of the beast (see Revelation 14:9 - 10). His punishments begin when the first of seven angels sounds a trumpet (Revelation 8:7). These miraculous judgments, as well as those killed during Christ's return, will cause several BILLION people to die (see Revelation 9:14 - 21, 14:20, etc.).