Contradiction with John 13:2
Contradiction with the notion of Judas as a devil from the beginning, showing that the devil entered into him later.
John 13:2: And supper being ended, the devil having now put into the heart of Judas Iscariot, Simon's [son], to betray him;
Contradiction with Mark 14:21
Contrasts the idea of predestined betrayal with the responsibility and woe upon Judas himself.
Mark 14:21: The Son of man indeed goeth, as it is written of him: but woe to that man by whom the Son of man is betrayed! good were it for that man if he had never been born.
Contradiction with Luke 22:48
Highlights Judas's conscious betrayal despite being one of the chosen, which contradicts his predestined role as implied in John 6:71.
Luke 22:48: But Jesus said unto him, Judas, betrayest thou the Son of man with a kiss?