Contradiction with Matthew 14:1-2
These verses suggest that Herod thought Jesus was John the Baptist risen from the dead, but don't specify Herod's direct admission, suggesting a kind of indecision.
Matthew 14:1-2: At that time Herod the tetrarch heard of the fame of Jesus, [tetrarch: or, governor over four provinces]
Contradiction with Luke 9:7-9
These verses depict Herod as perplexed about who Jesus was, hearing various opinions, thus reflecting uncertainty rather than the conviction shown in Mark 6:16.
Luke 9:7-9: Now Herod the tetrarch heard of all that was done by him: and he was perplexed, because that it was said of some, that John was risen from the dead;
Contradiction with John 1:19-21
These verses highlight John's distinction from other figures like Elijah or the prophet, which contrasts with Herod's seeming conflation of Jesus with John as suggested in Mark 6:16.
John 1:19-21: And this is the record of John, when the Jews sent priests and Levites from Jerusalem to ask him, Who art thou?