The word 'antichrist' is not used at all in the Book of Revelation. It's only found in the Bible in the writings of the Apostle John in 1 John and 2 John...

"This is the last hour; and as you have heard that the antichrist is coming, even now many antichrists have come." - 1 John 1:18
"Who is the liar? It is the man who denies that Jesus is (was) the Christ. Such a man is the antichrist." - 1 John 1:22
"Every spirit that does not acknowledge Jesus is not from GOD. This is the spirit of the antichrist, which you have heard is coming and even now is already in the world." - 1 John 4:3
"Many deceivers, who do not acknowledge Jesus the Christ as coming in the flesh, have gone out into the world. Any such person is the deceiver and the antichrist." - 2 John 1:7

These are the only five examples of the word 'antichrist' in Holy Scriptures. In The Revelation Chapter 13, the term is the "666 1st Beast" and "2nd Beast" which are commonly referred to as the Antichrist.

antichrist: one whose actions are the opposite of the Christ.

That's the simplest definition possible of the Antichrist or anyone who is an antichrist. Now it gets a little harder to define who exactly is an antichrist and who exactly was/is thee Antichrist.

Jesus son of Joseph was God-incarnate. He was thee teacher in history and according to Scriptures, he performed great miracles that no one else before or since has accomplished. He was thee great liberal in so much that he was trying greatly to change the very sinful status-quo of the rich, greedy, powerful and violent of them preying on the poor, weak, sick, and elderly. The Christ is thought of as treating and loving everyone equally.

So there you have the simplest explanation of Christ-like and Antichrist-like actions. The Revelation Chapter 13 identifies the "666 1st Beast as being the ruler of the world, lied to all nations and was wounded yet lived." It was only until Premier Mikhail (Michael) Gorbachev and the Soviet Union began to crumble and loose its influence around the world that there was a clear example of a true world leader: Ronald(6 letters) Wilson(6) Reagan(6). "He was given authority over every tribe, people, language and nation." - Rev 13:7.

Rev Ch 13 states three times that the "666 1st Beast will be wounded yet live". Reagan was shot just 69 days after being inaugurated in 1981 by John Hinckley, but he survived the assassination attempt.

Rev 13:1, "And I saw a beast coming out of the sea." Sounds like a vision of a submarine surfacing. Ronnie and Nancy Reagan were professional actors who only appeared in one movie together, Hellcats of the Navy (1957) which was based on the book Hellcats of the Sea (1955). Ronald played the submarine commander and Nancy played Helen the nurse.

The "7 heads" of Rev 13:1 are the 7 heads of state of the G7 Economic Conference. In 1983, Reagan hosted the G7 Summit in Williamsburg, VA.

"Had feet like those of a bear." - Rev 13:2. Reagan was from California and on the California State Seal, a grizzly bear is depicted.

Ronald Wilson Reagan was born on February 6 (2/6). Matthew 2:6, "For out of thee shall come a Governor, that shall rule my people Israel" (KJV). Reagan was Governor of California.

The Antichrist is usually connected to the "rider on the white horse" of Rev 6:2. Reagan was famously given a white horse by the Mexican president which Reagan rode around his ranch and loved to be photographed riding. Google: Ronald Reagan riding white horse (image).

Reagan's best known movie role - besides Bedtime for Bonzo - was as 'the Gipper' in Knute Rockne - All American. Rockne famously coached the "4 Horsemen" at Notre Dame in 1924.

When the Reagans left the White House in January 1989, they moved into their California ranch at 666 St. Cloud. Nancy immediately had the address changed to 668.

Note the simple(6) and consistent code of Step 1 of English(7) gematria(8)...

Ronald(6 letters) Wilson(6) Reagan(6) was the "666 1st Beast"/Antichrist.
George Walker Bush Jr. is the "2nd Beast/Antichrist who exercised all the power/authority of the 1st Beast.
United(6) States(6) Dollar(6) is the "666 mark of the Beast that everyone must have to buy or sell with".