2Thessalonians 2:7 For the mystery of iniquity doth already work: only he who now letteth will let; until he be taken out of the way.

Read 2Thessalonians 2:1-17 and Revelation 17:1-7,18.

Revelation 17:5 The whore’s name is MYSTERY and the Mystery of Iniquity of 2Thessaolonians 2:7 are the same. Mystery is the unknown. That which is unknown and unaccepted about salvation in Christ makes one a deceiver and an antichrist. 2John 7.

2John 7 – For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist.

Mystery of iniquity happens when we humans mature and come to know right from wrong and we chose to do wrong, we sin. At that point Sin becomes our Lord and master. All mature humans are guilty of this action. God set us up so that this would be our reality through the Law of Moses.Romans 5:20, 21.

Romans 5:20 – Moreover the Law entered, that the offence might abound. But where Sin abounded, Grace did much more abound;
5:21 – That as Sin hath reigned unto death, even so might Grace reign through righteousnes unto eternal life by Jesus Christ our Lord.

The whore, MYSTERY, is an imagined city that has real citizens. These citizens are those decevers who don’t confess that Jesus Christ has come in the flesh. These people are also known as antichrists. 2John7.
The rise of the Antichrist is a false statement, for there are many antichrists according to 2John7, and this has been true since Christ came in the flesh to earth.

As to the fulfilment of which we can see in current moves toward one world government?

One world goverment can’t effect a brother of Christ, not even death itself can do that. The worst that a sinful person or government can do to a brother of Christ is to kill us. Truth is, we as brothers of Christ are dead already in Christ Jesus. Romans 6:1-23.

Romans 6:3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
6:4 – Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
6:5 – For if we have been planted together in the likeness of his death, we shall be also in the likeness fo his resurrection:
6:6 – Knowing this , that our old man is crucified with him, that the body of Sin might be destoyed, that henceforth we should not serve Sin.
6:7 – For he that is dead is freed from Sin.