Here, the Apostle John resumes his analysis of the enemies to the Believer's fellowship with God. He reveals the nature of error in three verses. As mentioned in v.22, if you deny the deity (the Godness) of Jesus Christ is to deny the Trinity. One of the earliest heresies which is reflected here in 1 John 2 is that Jesus was nothing but a man upon whom the spirit of Christ came. And, as the Lord Jesus grew up and came to the day of His baptism, at that point, the Christ Spirit came upon him and dwelt within him. This heresy says that the Spirit remained with Jesus the man until that day when he was buried. This heresy obviously denies the incarnation, the fact announced in John's Gospel that "the word was made flesh," (John 1:14).
Now, John is not the only biblical writer to refer to the deity of the Lord Jesus, others do so, as well.
Paul called Jesus “our great God and Savior” (Titus 2:13) Thomas, one of the twelve disciples, called Jesus: “My Lord and my God!” (John 20:28)
Isaiah, the Old Testament prophet, said that the coming Messiah would be God. Isaiah 9:6 says, “For unto us a Child (a reference to His humanity) is born, unto us a Son is given; and the government will be upon His shoulder. And His name will be called Wonderful Counselor, Mighty God (a reference to His deity), Everlasting Father, Prince of Peace.”
GOD the Father called Jesus “God.” Hebrews 1:8 says, “But to the Son He (God the Father) says: ‘Your throne, O God, is forever and ever; a scepter of righteousness is the scepter of Your Kingdom.’” (Quoting Psalm 45:6-7)
It is obvious that the Lord Jesus was and is God. I turn your attention to John's gospel, chapter eight. Notice verses 44 through 46.

As in 1 John 2, John refers here to the Devil as a Liar. In context, the Lord Jesus is in a discussion with the religious leaders of the day. These leaders are trying to show up the Lord Jesus, and the Lord Jesus asks them a great question in verse 46. Notice it, "Can any of you prove me guilty of sin?" Notice their answer in verse 48 "The Jews answered him, “Aren’t we right in saying that you are a Samaritan and demon-possessed?” Did you notice that? Look at it again.
48 "The Jews answered him, “Aren’t we right in saying that you are a Samaritan and demon-possessed?” Do you see what they are not saying? They never answer His question about sin. Do you know why? They couldn't. The loudest display of Christ's divinity is their silence. Something to think about.