Contradiction with John 3:32
This verse states that no one receives Jesus’s testimony, which contradicts the acknowledgment in John 3:28 of John bearing witness about Jesus.
John 3:32: And what he hath seen and heard, that he testifieth; and no man receiveth his testimony.
Contradiction with John 5:31
Jesus says that if He bears witness of Himself, His witness is not true, contrasting the affirmation of John’s witness in John 3:28.
John 5:31: If I bear witness of myself, my witness is not true.
Contradiction with John 8:14
Jesus claims His testimony is true even if He bears witness of Himself, which appears to contradict the implication in John 3:28 that John's witness is needed.
John 8:14: Jesus answered and said unto them, Though I bear record of myself, [yet] my record is true: for I know whence I came, and whither I go; but ye cannot tell whence I come, and whither I go.
Contradiction with John 5:36
This verse mentions the greater witness of the works Jesus does, which challenges the focus on John's witness in John 3:28.
John 5:36: But I have greater witness than [that] of John: for the works which the Father hath given me to finish, the same works that I do, bear witness of me, that the Father hath sent me.
Contradiction with John 5:37
God’s own testimony of Jesus is noted, suggesting a more significant witness than John’s in John 3:28.
John 5:37: And the Father himself, which hath sent me, hath borne witness of me. Ye have neither heard his voice at any time, nor seen his shape.