This article is about a type of people. You may be looking for the Beast out of the Sea, called the "Antichrist".
An antichrist is a person who was once a part of the body of Christ, but were not really a part of it, and deny both Jesus and the Father. Had they really been a part of it, they wouldn't have left it. Those who say that Jesus has not really come in the flesh are also antichrists. Also, every spirit that says Jesus is not from God is a spirit of the antichrist. Many have titled the Beast out of the Sea as "the Antichrist", as if there is only one who deserves that title and it that beast, although John the Apostle makes it clear that anyone can be an antichrist, although he does not recommend it whatsoever.
The term antichrist comes from the Greek word ἀντίχριστος (transliterated:"antichristos"), which means "opponent of the Messiah". Ἀντίχριστος comes from the two Greek words ἀντί (transliterated: anti) and Χριστός (transliterated: Christos). Ἀντί means "opposite". Χριστός means "anointed or Messiah (Christ)".