Who is the Antichrist?
The Answer of the Bible
The Antichrist is not just one person or organization, for the Bible says that "many have become antichrists" (1 John 2:18). The word "antichrist" comes from the Greek and means "against (or: instead of) Christ." It denotes all who ...

deny that Jesus is the Christ (Messiah) and the Son of God (1 John 2:22)
oppose Christ, the anointed of God (Psalm 2:1, 2; Luke 11:23)
impersonate Christ (Matthew 24:24)
persecute Christ's disciples, because Jesus takes that personally (Acts 9:5)
Claim to be Christians but do not obey laws or deliberately deceive others (Matthew 7:22, 23; 2 Corinthians 11:13)

However, the Bible does not only refer to individuals who do such things as antichrists. The Bible also refers to all such individuals as a whole by the term "the Antichrist" (2 John 7). The Antichrist appeared in the first century and has been active throughout ever since. This development was already predicted in the Bible (1 John 4:3).
How to recognize antichrists

They spread false views about Jesus (Matthew 24:9, 11). For example, those who teach the Trinity or claim that Jesus is Almighty God are actually saying the opposite of what Jesus taught, "The Father is greater than I" (John 14:28).
Antichrists contradict what Jesus said about how the Kingdom of God should be approached. For example, some ministers claim that Jesus would accomplish his goals with the help of today's governments. But Jesus clearly said, "My kingdom is no part of this world" (John 18:36).
They call Jesus their Lord but do not keep his commandments, such as the mandate to preach the good news of the kingdom of God (Matthew 28:19, 20; Luke 6:46; Acts 10:42).