Does not Paul teach that Jesus will destroy the antichrist - the man of sin - upon his return to earth?
I assume you are referring to:
"And then the lawless one will be revealed, whom the Lord will consume with the breath of His mouth and destroy with the brightness of His coming." (2 Thess 2:8)
The Lord Will ConsumeAnd then the lawless one will be revealed, whom the Lord Jesus will overthrow with the breath of his mouth and destroy by the splendor of his coming. The coming of the lawless one is according to the working of Satan, with all power, signs, and lying wonders. (2 Thess. 2:8-9)[32]
As just indicated, the lawless one was eventually openly revealed. The mystery form of his character gave way to a revelation of his lawlessness in Nero's wicked acts. This occurred after the restrainer [Claudius, who maintained religio licita] was "taken out of the way," allowing Nero the public stage upon which he could act out his horrendous lawlessness.
According to Hendriksen verse eight destroys any preterist interpretation identifying the Man of Lawlessness with the Roman emperor, because it ties the events to the era of the Second Advent.[33] The strong preteristic indications in the passage heretofore, however, demand a different understanding of the destructive coming of Christ here mentioned. As already shown in the discussion of verse 1, Matthew 24:30 is most relevant here: "Then the sign of the Son of Man will appear in heaven, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory." And that verse is specifically applied to the first century (Matt. 24:34), as is Revelation 1:7[34] (cp. Rev. 1:1, 3); Matthew 26:63-65; and Mark 9:1. Christ comes in judgment upon Jerusalem in the events of A.D. 67-70.
In that judgment-coming against Jerusalem there is also judgment for the Man of Lawlessness, Nero. There is hope and comfort in the promised relief from the opposition of the Jews and Nero (2 Thess. 2:15-17). Not only was Jerusalem destroyed within twenty years, but Nero himself died a violent death in the midst of the Jewish War (June 8, A.D. 68). His death, then, would occur in the Day of the Lord in conjunction with the judgment-coming of Christ. He will be destroyed by the breath of Christ, much like Assyria was destroyed with the coming and breath of the LORD in the Old Testament (Isa. 30:27-31) and like Israel was crushed by Babylon (Mic. 1:3-5). In fact, by God's providence Nero's death stopped the Jewish War briefly so that Christians trapped in Jerusalem could escape (cp. 1 Thess. 1:10).[35] The Man of Lawlessness/Beast, Nero Caesar, dies in the Day of the Lord with the Great Harlot, Jerusalem (Rev. 19:17-21; cf. Rev. 22:6, 10, 12).
The Man of Lawlessness: A Preteristic Postmillennial Interpretation of 2 Thessalonians 2 by Dr. Kenneth L. Gentry, Jr.
Notes:
[32]Such imperial arrogance would produce alleged miracles as confirmation. Vespasian is called "the miracle worker, because by him "many miracles occurred." Tacitus, Histories 4:81; Suetonius, Vespasian 7. Notice that Paul speaks of these as "lying wonders."
[33]Hendriksen, I and II Thessalonians, 173.
[34]See my Before Jerusalem Fell: Dating the Book of Revelation (Tyler, Tex.: Institute for Christian Economics, 1989), ch. 8.
[35]See: Josephus, Wars 4:11:5. Cp. Luke 21:18, 20-24, 27-28; Eusebius, Ecclesiastical History 3:5:3; Epiphanius, Heresies 29:7. See also: Rev. 7:1-17 in Gentry, Before Jerusalem Fell, 243-244.
(This article is very long, but you need to conmsider it carefully see all the implications.)