According to 1 John, anyone who denies that Jesus is the Christ, that he is the unique Son of God, or that he has come in the flesh. The biblical term, however, primarily refers to a particular person who becomes a significant denier in the final stage of history.
The word “antichrist” occurs only four times, all in John’s letters (1 John 2:18, 22; 4:3; 2 John 1:7). First John 2:18 refers also to “many antichrists.” John assumed that his Christian readers knew about the Antichrist and had been taught to expect his coming (1 John 2:18–27). The presence of many antichrists indicated that the end times had arrived. But John warned that a final Antichrist would appear and deny that Jesus is the Christ.
John said anyone or message that did not “confess Jesus” is of the spirit of the antichrist (1 John 4:3). John's second letter describes “many deceivers” who would not acknowledge the coming of Jesus Christ in the flesh (2 John 1:7). Such a person was “the deceiver and the antichrist.”