Modern theologians who subscribe to the theology set forth in the Left Behind novels, believe that there will be a Devil incarnate - a man who will be Satan in the flesh. In the Left Behind novels, his name is Nicolae Carpathia. To get this idea of a single Mr. Diabolical, a way of reading the Bible called Dispensationalism is necessary.
Dispensationalism divides history (and the Bible) into, what else?, dispensations. Basically put, this interpretation says that God has dealt with humanity in different ways, at different times. There are seven dispensations, but they are not chronological. Sometimes one dispensation is suspended while another begins and is picked up again later. Some of these dispensations include the Dispensation of Law, of Conscience, of Innocence, and of Government. This idea has never been supported by scholars or those who know how the Bible came into existence. It was invented by a man named James Darby in the 1800's. The rapture idea followed because it was impossible to see how God's people who had received grace to experience a time of tribulation, spoken of by Jesus and written about by Paul.
In order to fit the Bible into these dispensations, you have to string texts together that had nothing to do with one another originally. Because of this, the apocalypse in Daniel (ch. 7-12) and the Book of Revelation then can be read as a single work.
This is where modern theologians get their notions about the Antichrist - by stringing together texts in the Bible that orginally had nothing to do with one another. Drawing on references to Antiochus Epiphanes IV and the Beasts in Revelation 13 - one can sculpt a disturbing mold of a future Mr. Dictator. However, this is not supported by a reading of Revelation that takes into account it's historical or literary context. Each author of a Biblcal book wrote for a specific purpose to a specific group of people. The canon as we know it did not exist - the authors did not base their works on what we now know as the Christian canon, but on what they believed about Jesus and God.
John wrote to an audience that understood what he meant, and his writing of Revelation had importance in their eyes - after all, they preserved his letter. First, John writes about two beasts. The first beast is Roman Imperial Power, and specifically (I believe) Nero. This is made obvious by the 'mortal wound' comment in Rev. 13.3. It is in line with a Nero tradition that his death was a ploy to further persecute those who didn't support him. The second beast (v. 11), is the Emperor Cult, who would force worship of the first beast. The first is out of the water... the second is out of the earth. This is consistent with the water evoking thoughts of terror, and the earth meaning the place from which things come. The Emperors were elevated to "god" status by the cult, which forced worship of them from all.
The problem obviously presents itself for Christians, who are supposed to worship only God. This is the point of John's writing. Christians were being coerced into worshipping the Emperor, but John is telling them not to assimilate into Roman Imperial Culture. He knows that it will hurt them financially if they do not participate (v. 17), so many are compromising their faith and worshipping the Emperor. He is writing to discourage this.
Further, the Bible does talk about Antichrist, but there are many not one. Antichrist figures are also common in apocalyptic literature, especially preceding the eschaton. 1 John speaks of many, Matthew 24 speaks of many, there is not one Mr. Diabolical at the end of time, but many will precede the end. I do believe that John saw Roman Imperial Power as being endowed by Satan (v. 2), and that he saw Nero as Satan's pawn. But John did not limit the role of Antichrist to Nero, he simply pointed out that he was one of many.
Also in this series:
THE BOOK OF REVELATION: PART 2
THE BOOK OF REVELATION: PART 1
THE NATURE OF PROPHECY