Contradiction with Matthew 28:5-6
Jesus had risen, and the women found the tomb empty early in the morning, contrasting with John 20:19 saying it is evening when Jesus first appears to the disciples.
Matthew 28:5-6: And the angel answered and said unto the women, Fear not ye: for I know that ye seek Jesus, which was crucified.
Contradiction with Mark 16:14
Jesus appears to the disciples as they sat at meat, unlike John 20:19 which suggests they were hiding behind closed doors.
Mark 16:14: Afterward he appeared unto the eleven as they sat at meat, and upbraided them with their unbelief and hardness of heart, because they believed not them which had seen him after he was risen. [at meat: or, together]
Contradiction with Luke 24:36-37
The disciples were startled and frightened by Jesus' appearance, unlike the calm reception implied in John 20:19.
Luke 24:36-37: And as they thus spake, Jesus himself stood in the midst of them, and saith unto them, Peace [be] unto you.
Contradiction with Acts 1:3
Mentions Jesus appearing over forty days with many proofs, as opposed to the singular peaceful event in John 20:19.
Acts 1:3: To whom also he shewed himself alive after his passion by many infallible proofs, being seen of them forty days, and speaking of the things pertaining to the kingdom of God: