"It is certain that Antichrist will be a man because the Scriptures call him in express terms the "man of sin..." It is certain that he will be of the Jewish race....Like Our Lord, he will be brought up in obscurity; he will lead a hidden life until the time comes when he shall begin his public career....According to tradition, he will be educated by magicians who will imbue his mind and heart from his very childhood with their doctrine and wicked principles...
He shall never do a good act. His satanic pride shall be especially conspicuous...He will conceal his crimes and pass as the most virtuous of men...He will be loaded with honors...He will possess a natural, vast, and powerful genius, an irresistable eloquence...He will know by heart all the Sacred Scriptures and posses a perfect knowledge of the arts."
No one would believe me if I told them, but I think I've had certain experiences that gave me insight into the Anti-Christ.
I will just add some things to this prophecy, which I think is pretty accurate.
Anti-Christ will sit not just in the place of God, in terms of imitating Christ, but in the place of the Church. He will convince the world the Church is dead, except for himself and his followers, and he will use the failings of the clergy to make this believable ( many of the clergy at that point, like today, will be immoral or borderline-heretics and the truth will be hard to find all in one place ).
He will essentially set himself up as THE Church in the form of a man -- he will make people believe that they should actually leave their chapels and follow him instead, using, once again, the failings of the clergy to make this convincing.
That is where the sign comes in, as a way of showing obedience to him. He will kill those who disagree with him even in the slightest and will cause great fear in everyone. People who try to get his approval and kiss up to him even will be randomly massacred, it will be like being in the Mafia. He will become more arbitrary and more erratic as time goes on.
As has been said by many, his life will mirror episodes in the life of Christ. For instance, he will be stripped and "humiliated" like Christ was, but instead of being cruficied afterwards, he will rise up more powerful. He and the false prophets who surround him will arrange it that he is stripped and humiliated precisely for this purpose. It will be aesthetic, artistic -- he will be like a concept-artist version of Christ who will trump up for himself some of the things that happened to the real Christ by Divine Providence. Like a David Bowie kind of showman but who genuinely presents himself as a Messiah.
I will also predict that he will disdain the false prophets who surround him. They will build him up, but he will think he's doing it all himself and doesn't need them. He will think he is totally one of a kind and unique, not realizing that he is part of a vast diabolical team.
He will be way younger and prettier and have infinitely more charisma and charm than JPII, let alone Ratzinger. He will look like a saint and will have such magnetic and fascinating personal presence that it will be mistaken for holiness. He will be the ultimate movie star, basically. He will be as charming as a lamb but will switch into terrifying dragon-like anger.