Contradiction with John 1:29
Matthew 11:2 shows John the Baptist doubting, while John 1:29 depicts him confidently proclaiming Jesus as the Lamb of God.
John 1:29: The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world. [taketh away: or, beareth]
Contradiction with Luke 7:20
Similar to Matthew 11:2, but some interpret the query differently from Luke, indicating John's unclear faith.
Luke 7:20: When the men were come unto him, they said, John Baptist hath sent us unto thee, saying, Art thou he that should come? or look we for another?
Contradiction with John 3:30
John the Baptist expresses certainty in Jesus' mission, contradicting his doubt in Matthew 11:2.
John 3:30: He must increase, but I [must] decrease.