What is the spirit of antichrist? In 1 John 2:18, why does it say antichrists?
The spirit of antichrist is the devil working through the world system, politics, economics, and religion. Antichrist comes from two Greek words, anti (against) Christos (Christ, Messiah). Anything that is “against Christ” has the spirit of antichrist.
John also tells us that the spirit of antichrist has to do with denying Jesus Christ as well as the rest of the Godhead (1 John 2:22-23). In denying the Persons of the Godhead a person with the spirit of antichrist will deny everything else that is truthful about them from their words to their actions.
Anything that raises itself up against God and the things of God is considered antichrist. You can see that the devil has his hand in everything. This will make it easier for the antichrist to rise to power.
All the destruction and death and pestilences flow from the spirit of antichrist. The world order and world system will be brought about because of the underlying spirit of antichrist. It is in this spirit that the antichrist will rise to political and religious power and create the one world order. The spirit that is in the world will be happy that the antichrist rises to power.
As for your second question, why is the word for antichrist plural in 1 John 2:18? The reason it is plural in the context of 1 John is that he is speaking about false teachers and false prophets who have been kicked out of the church. He says that they came from us but were not of us (1 John 2:19).
Besides false teachers and prophets, there are multiple people in the world whether they be rulers or people in high places of religion, society, or anywhere else who are against Christ in their words or actions who are antichrists. They are usually in places of power because the antichrist seeks to be in charge. He does not do well with submission to authority of any kind.
My personal belief is that there are multiple antichrists in our world in every generation and in every area of the world. These are people ready to rise to power the moment that the rapture happens and the church and the Restrainer leave this earth. That will be the queue for the antichrist to take his place of power and begin the Great Tribulation of the end times.
Why are there multiple people ready to rise to the status of the antichrist? Jesus was clear that no one knows the day or time that he will return to the earth for his Church (Matthew 24:36; Mark 13:32; Acts 1:7). We must not forget that Satan is not all-knowing, all-powerful, or everywhere present.
He must have his people in place so that one of them can rise to power as the antichrist when Jesus returns. Since he doesn’t know when that time is he must be prepared in every generation. This is why people declare things like Hitler and other world leaders are the antichrist. They could be right for that generation. We don’t know what evil plans the devil has in place may be.
This is another possible reading of what John means by antichrists. In his generation, it was most likely Roman emperors like Domitian and Nero. Both of them were persecutors of Christians to the max. And they were in the perfect place to take over the world if Christ had returned in that generation.