Thank you for your question.
Antichrist is the translation of the Greek word antichristos literally meaning ‘opposite to or instead of Christ (anointed).
The word is used in the Bible just 5 times only, by John:
1. 1John 2:18 Little children, it is the last time: and as ye have heard that antichrist shall come,
2. even now are there many antichrists; whereby we know that it is the last time.
3. 1John 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.
4. 1John 4:3 And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world.
5. 2John 1:7 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.
From 2 we see that there are many antichrists not just one.
From 3 we see that anyone who denies that Jesus is the Christ (Messiah or anointed one) or denies the existence of both God and his son is antichrist.
From 4 and 5 we see that anyone who denies that Jesus Christ is come in the flesh (ie was born as a human being) is antichrist.
I hope this helps