Who is the Beast of Revelation? In this Seven Minute Seminary video, Dr. Ben Witherington responds with important Bible background.
It's important to keep in mind that the term "antichrist" actually only shows up in the epistles of John (1 John 2:18-22; 4:3; 2 John 1:7), where there are supposedly several antichrists already on the scene. Christians have conflated this term with one of the beasts in Revelation though, who has the famous number 666 (Rev. 13:18). Using gematria, an ancient numerical code system for concealing sensitive information, the biblical author was referring to "Nero Caesar, the Son of the Divine Augustus," which in Latin has the numerical value of 666. In the 90s, some even thought that the emperor Domitian was Nero come back from the dead.
So Revelation teaches that the beast, or person who sets himself up against Christ and his church, is a Nero-like figure. Human history tends to repeat itself and may even culminate in a figure whose character resembles that of Nero.