The term ‘antichrist’ appears in 1 John 2:18, 2:22, 4:3 as well as 2 John 1:7. From these verses, it is clear that ‘antichrist’ is defined as anyone who denies that Jesus is the Christ. The term ‘Christ’ is the Greek counterpart to the Hebrew term ‘Messiah.’ The Apostle John mentions that there is a spirit called 'the spirit of the antichrist’ which was evidently already in the world and had produced many antichrists.
Children, it is the last hour; and just as you heard that antichrist is coming, even now many antichrists have appeared; from this we know that it is the last hour. (1 John 2:18, NASB)
Who is the liar but the one who denies that Jesus is the Christ? This is the antichrist, the one who denies the Father and the Son. (1 John 2:22, NASB)
and every spirit that does not confess Jesus is not from God; this is the spirit of the antichrist, of which you have heard that it is coming, and now it is already in the world. (1 John 4:3, NASB)
For many deceivers have gone out into the world, those who do not acknowledge Jesus Christ as coming in the flesh. This is the deceiver and the antichrist. (2 John 1:7, NASB)
However, in one sense, John was blending the teachings found in passages like Matthew 24:23-24 with 2 Thessalonians 2:1-12 and applying them to his time.
In Matthew 24:23-24, talking about the signs of the end of the age, Jesus mentions that false Christs and false prophets will appear and perform great signs and wonders to deceive people.
In 2 Thessalonians 2:1-2, Paul tells the Thessalonians that no one should be deceived in any way to believe that the day of the Lord was already here. Paul goes on to say, in verses 3, that the day of the Lord will not arrive until a falling away from the faith occurs and the ‘man of lawlessness’ or the ‘son of destruction' be revealed.
In verse 4, we learn a little bit about this 'man of lawlessness.’ We are told that he will oppose and exalt himself above every so-called god or object of worship and that he will take his seat in the temple of God displaying himself to be God. In verse 5-6, Paul mentions that he previously talked about the power that is holding back the ‘man of lawlessness’ so that he will be revealed in his own time. This restrainer is evidently the Holy Spirit which will allow the man of lawlessness to go about his business at a future point in time. I used to believe it was to be equated with the alleged removal of the Holy Spirit after a pre-tribulation rapture, but I no longer believe in a pre-tribulation rapture.
In verse 7, Paul interestingly distinguishes between the power of lawlessness which is already at work, and the lawless one which will be revealed after the restrainer is removed. The similarity here between the ‘power of lawlessness’ and the ‘spirit of the antichrist’ mentioned by John is very evident. Therefore, the ‘lawless one’ parallels a singular Antichrist who will be revealed.
Verses 9-12 then conclude the topic with Paul talking about how the lawless one will come by Satan’s working with all kinds of signs, false wonders, and every kind of deception. The terms used here are the very terms that Jesus uses when He talks about false Christs and false prophets. We are told that the lawless one will direct this at those who are unsaved because they did not have the love of the truth in their heart through which they would have been saved. God will send them a deluding influence so they will believe what is false, and because they did not believe the truth but delighted in evil they will be condemned.
The Bible tells us more about the coming Antichrist in the Book of Daniel and the Book of Revelation.
In Daniel 7, Daniel has a dream of four beasts. I won’t go through the characteristics and fulfilment of the four beasts in detail so I’ll leave a link to a gotquestions.org article which is accurate for the most part (Link).
The first beast was like a lion. (Babylonian Empire)
The second beast was like a bear. (Medo-Persian Empire)
The third beast was like a leopard with four heads. (Grecian Empire)
The fourth beast was characterized by things such as its ten horns. (Roman Empire)
In the dream, Daniel saw a little horn come up and pluck out three of the ten horns. In Daniel 7:23-25, the angel explains the meaning behind the little horn.
Thus he said: ‘The fourth beast will be a fourth kingdom on the earth, which will be different from all the other kingdoms and will devour the whole earth and tread it down and crush it. As for the ten horns, out of this kingdom ten kings will arise; and another will arise after them, and he will be different from the previous ones and will subdue three kings. He will speak out against the Most High and wear down the saints of the Highest One, and he will intend to make alterations in times and in law; and they will be given into his hand for a time, times, and half a time. (Daniel 7:23-25, NASB)
The Antichrist is the little horn who will reign for the second three and a half years of the seven years of tribulation. The phrase ‘times, times, and half a time’ is representative of three and a half years. A 'time’ is one year, 'times’ is two years, and 'half a time’ is half a year. The same terminology is also found in Revelation 12:14 where it talks about the woman being nourished in the wilderness during three and half years of tribulation. I was taught that this referred to the first three and a half years of the seven years which was supposedly to be against 'left behind' Christians who the woman allegedly represented However, that is not the case. The Antichrist has to first speak out against the Most High according to Daniel 7:25, which is the event known as the abomination of desolation spoken of in Matthew 24:15/Mark 13:14/Luke 21:20 and Daniel 9:27 which occurs mid-way through the seven years. Furthermore, Matthew 24:16/Luke 21:21 notably mentions that those in Judea would 'flee' to the mountains.
Then the woman fled into the wilderness where she had a place prepared by God, so that there she would be nourished for one thousand two hundred and sixty days. (Revelation 12:6, NASB)
"Therefore when you see the ABOMINATION OF DESOLATION which was spoken of through Daniel the prophet, standing in the holy place (let the reader understand), then those who are in Judea must flee to the mountains. (Matthew 24:15-16, NASB)
In total, the four beasts have seven heads and ten horns. The first beast in Revelation 13 is said to have seven heads and ten horns. In fact, it is described as having aspects of a leopard, a bear, and a lion. Thus, the fourth beast of Daniel 7 is the first beast in the Book of Revelation and will borrow aspects of the other three empires.
And the dragon stood on the sand of the seashore. Then I saw a beast coming up out of the sea, having ten horns and seven heads, and on his horns were ten diadems, and on his heads were blasphemous names. And the beast which I saw was like a leopard, and his feet were like those of a bear, and his mouth like the mouth of a lion. And the dragon gave him his power and his throne and great authority. (Revelation 13:1-2, NASB)
The second half of Revelation 13 talks about the false prophet who will bring support to the Antichrist. With this in mind, Revelation 17 is interesting. It talks about the harlot of Babylon sitting on the first beast who has seven heads and ten horns. The seven heads we are told signify seven mountains on which the woman sits. The seven heads also signify seven kings or kingdoms.
And he carried me away in the Spirit into a wilderness; and I saw a woman sitting on a scarlet beast, full of blasphemous names, having seven heads and ten horns. (Revelation 17:3, NASB)
“The beast that you saw was, and is not, and is about to come up out of the abyss and go to destruction. And those who dwell on the earth, whose name has not been written in the book of life from the foundation of the world, will wonder when they see the beast, that he was and is not and will come. Here is the mind which has wisdom. The seven heads are seven mountains on which the woman sits, and they are seven kings; five have fallen, one is, the other has not yet come; and when he comes, he must remain a little while. The beast which was and is not, is himself also an eighth and is one of the seven, and he goes to destruction. The ten horns which you saw are ten kings who have not yet received a kingdom, but they receive authority as kings with the beast for one hour. These have one purpose, and they give their power and authority to the beast. (Revelation 17:8-13, NASB)
Many commentators identify the seven mountains with the seven hills of Rome. Thus, they believe that the harlot woman which is the apostate church is linked with the Roman Catholic Church.
When looking at it from the perspective of seven kings or kingdoms, we are told that five have fallen, one is, and the other is yet to come. The following kingdom will only last a little while and the leader is a man, the Antichrist, who is considered the eighth king even though he belongs to one of the seven kingdoms. We cannot take the seven heads in Daniel to be the same seven heads here. If the four heads of the third beast in Daniel were considered kingdoms, six kingdoms should have been considered fallen by the time John was writing because Rome was in power. It is more likely that four of the seven heads in Revelation line up with the four beasts in Daniel. Since we know five had fallen by the time John was writing, the first three beasts of Revelation correspond to the third, fourth, and fifth heads in Revelation. Taking Isaiah 52:4 and other factors into account, the seven kingdoms would be the Egyptian Empire, the Assyrian Empire, the Babylonian Empire, the Medo-Persian Empire, the Grecian Empire, the Roman Empire, and the coming Revived Roman Empire. From the Revived Roman Empire, the Antichrist’s Empire will rise. The ten horns link back to ten horns described in Daniel 7.