For clarification and the forward movement of the thread.
From the website of the Wisconsin Evangelical Lutheran Synod:
John says that there are many antichrists - that is, many who deny that Jesus Christ is God who came in the flesh (1 John 4:2-3). These antichrists are not the same antichrist that Paul spoke about in 2 Thessalonians 2.
Some of the characteristics of the antichrist in 2 Thessalonians 2 that identify the antichrist as the papacy are these:
2 Thessalonians 2:3 he would be associated with a rebellion (a falling away) and he would be the man of lawlessness - the leader of this sinful falling away. = this Antichrist would lead many people away from Christ.
2 Thessalonians 2:9-10 this falling away, led by the lawless one (the rebel) would be the work of Satan, marked by conterfeit (i.e. things that deceive people) miracles of various kinds done with Satan’s power to deceive people so that they refuse to believe the truth that salvation was won for us by Christ and refuse to be saved by faith in him alone = this Antichrist would teach a way of salvation which denies that salvation is by faith alone in Jesus.
2 Thessalonians 2:4 he would exalt himself above everything that is called God and worshipped (i.e. everyone who is to be honored as God’s representative in the family, government, and church) and proclaim himself to be God (cf. the papacy’s claim that the Pope speaking officially speaks the word of God) and that everyone must be subject to the Pope to be saved = this Antichrist would set himself up over all of the God-given representatives and insist that salvation could be had only by accepting his authority.
2 Thessalonians 2:7 the secret power of this lawlessness was already at work at Paul’s time (i.e. the denial of salvation by faith in Jesus alone). 2 Thessalonians 2:6 this lawlessness would be held in check by the word of God until he would be revealed (i.e. he would teach his lawlessness openly as indicated in the comments on vv9-10 and v4 above), 2 Thessalonians 2:8b eventually his stranglehold on the family, government, and church would be broken by the breath of Jesus’ mouth (i.e. the truth of the word of God again being openly proclaimed) - 2 Thessalonians 2:8c and he will be completely destroyed at the time when Jesus comes in splendor at the end of the world = this Antichrist was in its early development already at Paul’s time, he would grow in power until he openly taught his own way of salvation, his power would be broken by God’s word being taught openly again, but his rule over his followers would continue until the end of the world (N.B. this antichrist spans the entire history of the NT time)
2 Thessalonians 2:11-12 God’s judgment on the followers of this lawless man (who accept what this man teaches about the way of salvation) would be to give them over to a delusion that this man was God’s spokesman, a delusion so powerful that they can’t see the lie of this lawless man and reject the truth that God clearly teaches in his word = the followers of this Antichrist would become so blind that, even when they clearly see the truth of God’s word from the Bible, they don’t believe it but choose to follow his wicked, destructive doctrine instead.
The combination of these factors (his leading a large number of believers away from the truth, his denial of the truth of salvation, his claiming the preeminence over all God-given representatives and making the acceptance of his position a qualification for salvation, his existence spanning the whole NT period, the blindness of his ardent followers to the clear words of Scripture about salvation) are fulfilled in one person - the person who serves in the office of the Papacy.