Who is the Antichrist?
The Antichrist is the end times "man of sin" and "son of perdition," the Beast empowered by Satan the dragon, who exalts himself above every god, persecutes the saints and Israel for three and a half years, and demands worship as God.
Scripture describes the Antichrist as a man of fierce countenance who rises in the latter time, described in Daniel as one who understands dark sentences, whose power is not his own but comes from Satan, the dragon. He is called the man of sin and the son of perdition in 2 Thessalonians, the one revealed after a falling away, who exalts and magnifies himself above every god and speaks marvellous things against the God of gods, prospering until the appointed indignation is accomplished.
He is pictured in Revelation as the Beast rising out of the sea with seven heads and ten horns bearing names of blasphemy, given his power, his seat, and great authority directly by the dragon. One of his heads is wounded to death and healed, causing the whole world to marvel and worship him. He speaks great blasphemies and is given authority to continue for a set time, and it is given to him to make war with the saints and overcome them, with power given him over all peoples, tongues, and nations.
This figure is also the same spirit of antichrist that was already at work in the world, the spirit that entered Judas and caused him to betray Christ, the spirit that stirred the rulers of that day to crucify Jesus, and the same spirit that inspired the persecution of the early church. In the last days that spirit is manifested fully in a man, the Antichrist, who betrays those at peace with him: his words are smoother than butter, yet war is in his heart, and he breaks covenant with those he deceives. He will not regard the God of his fathers nor any other god, for he magnifies himself above all, honoring instead a strange god with gold, silver, and precious things.
He sets up the abomination of desolation, an idol in the holy place, stopping the daily sacrifice and causing the temple worship of Christ to cease. He causes craft to prosper in his hand, bringing economic control through the mark of the beast so that none may buy or sell without it, and he wars against Israel, subduing two thirds of that nation. His reign of terror against the saints and against Israel lasts for a time, times, and the dividing of time, that is, three and a half years, until he himself is broken without hand.
The scriptures
And in the latter time of their kingdom, when the transgressors are come to the full, a king of fierce countenance, and understanding dark sentences, shall stand up. And his power shall be mighty, but not by his own power: and he shall destroy wonderfully, and shall prosper, and practise, and shall destroy the mighty and the holy people. And through his policy also he shall cause craft to prosper in his hand; and he shall magnify himself in his heart, and by peace shall destroy many: he shall also stand up against the Prince of princes; but he shall be broken without hand.
And he shall speak great words against the most High, and shall wear out the saints of the most High, and think to change times and laws: and they shall be given into his hand until a time and times and the dividing of time.
And the king shall do according to his will; and he shall exalt himself, and magnify himself above every god, and shall speak marvellous things against the God of gods, and shall prosper till the indignation be accomplished: for that that is determined shall be done. Neither shall he regard the God of his fathers, nor the desire of women, nor regard any god: for he shall magnify himself above all. But in his estate shall he honour the God of forces: and a god whom his fathers knew not shall he honour with gold, and silver, and with precious stones, and pleasant things. Thus shall he do in the most strong holds with a strange god, whom he shall acknowledge and increase with glory: and he shall cause them to rule over many, and shall divide the land for gain.
Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
He hath put forth his hands against such as be at peace with him: he hath broken his covenant. The words of his mouth were smoother than butter, but war was in his heart: his words were softer than oil, yet were they drawn swords. Cast thy burden upon the LORD, and he shall sustain thee: he shall never suffer the righteous to be moved. But thou, O God, shalt bring them down into the pit of destruction: bloody and deceitful men shall not live out half their days; but I will trust in thee.
And I stood upon the sand of the sea, and saw a beast rise up out of the sea, having seven heads and ten horns, and upon his horns ten crowns, and upon his heads the name of blasphemy. And the beast which I saw was like unto a leopard, and his feet were as the feet of a bear, and his mouth as the mouth of a lion: and the dragon gave him his power, and his seat, and great authority. And I saw one of his heads as it were wounded to death; and his deadly wound was healed: and all the world wondered after the beast. And they worshipped the dragon which gave power unto the beast: and they worshipped the beast, saying, Who is like unto the beast? who is able to make war with him? And there was given unto him a mouth speaking great things and blasphemies; and power was given unto him to continue forty and two months. And he opened his mouth in blasphemy against God, to blaspheme his name, and his tabernacle, and them that dwell in heaven. And it was given unto him to make war with the saints, and to overcome them: and power was given him over all kindreds, and tongues, and nations.
And he shall confirm the covenant with many for one week: and in the midst of the week he shall cause the sacrifice and the oblation to cease, and for the overspreading of abominations he shall make it desolate, even until the consummation, and that determined shall be poured upon the desolate.
And arms shall stand on his part, and they shall pollute the sanctuary of strength, and shall take away the daily sacrifice, and they shall place the abomination that maketh desolate.
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.