As a consequence of the reaping of the angel, who is told to reap the earth (Rev 14:18-19), and the life threatening implications of the bowl plagues, no human beings survived Armageddon (Rev 16:1-21; 19:11-21).

Daniel prophesizes that by the end of the 70th week, sin will end (Dan 9:24). Since human beings are born with sin, the end of sin is only possible with the end of human beings.

After the Antichrist and False Prophet were thrown into the lake of fire, "the rest were killed with the sword which came from the mouth of Him who sat on the horse, and all the birds were filled with their flesh." (Rev 19:21)

All who remain on earth are angels who, because of their fallen state, are confined to earth (Rev 12:7-9).

Reigning with Jesus Christ during the Millennial Kingdom are the Great Tribulation saints "who had been beheaded because of their testimony of Jesus and because of the word of God, and those who had not worshiped the beast or his image, and had not received the mark on their forehead and on their hand" (Rev 20:4).

These saints, the first resurrection of Believers, are the first to complete their process of resurrection which occurs at the start of the Millennial Kingdom (Rev 20:4), and they are "blessed and holy" and "over these the second death has no power" (Rev 20:6).

Special because of their stalwart perseverance during this unique period of harsh persecution of their faith, these Believers were honored with authority to reign as priests of God and of Christ with Jesus during the Divine Millennial Kingdom (Rev 20:4). An example of these martyred Believers are those seen under the alter (Rev 6:9-11).

Satan’s imprisonment and removal of his evil influence from his fallen angelic followers may serve a redemptive purpose. Through the atonement of Jesus Christ, all things in heaven and earth were reconciled with God (Col 1:19-20), which seems to include fallen angels. But the writer of Hebrews indicates that Jesus' atonement does not help angels (Heb 2:16-17).

After the millennium, the apostle John reveals that Satan will be released from the Abyss to deceive again (Rev 20:7-8).

In the final war with Satan, no human military tactic is used; instead, heavenly fire consumes the enemy (Rev 20:7-9). Brimstone, which also originates from heaven (Gen 19:24; Ezek 38:22), supplies the lake of fire and is the means to eliminate Satan forever (Rev 20:10).

For deeper study:

The Millennium and the Judge