The word "antichrist" occurs five times in the Bible, four times in 1 John and once in 2 John.

Little children, it is the last time: and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time. 1 John 2:18

Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son. 1 John 2:22

Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son. 1 John 4:3

For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist. 2 John 1:7

Two things are clear from these verses:

The author of 1 John believed that the end of the world was coming soon - during his lifetime. He "knew" this because the antichrist would come just before the last time. And there were many antichrists when 1 John 2:18 was written.

Anyone who denies that Jesus is the messiah is an Antichrist. So that would include me and about six billion or so others who are now living.

Here's a Dan McClellan video about some of the many false things that are often said about the antichrist.