Jesus called Judas a devil and Peter satan, since they were yet acting in their carnal nature and mind, and those that be of men.
Yet scripturally Peter received from GOD the FATHER revelation about Jesus as the Messiah, than Judas who continued in the same manner.
Jesus prevented satan's request from testing Peter, but as for Judas Jesus allowed satan to enter later for the betrayal take place.
Judas since the beginning probably been skeptical that Jesus is the true promised Messiah, probably not whom he pictured to be carnally.
And he also probably continued with many conflicting thoughts while serving Jesus and the Kingdom of GOD.
As a result towards the end even had the thought to betray Him and get money in return.
But Peter had no such thought, but were confused and perceive not, many of Jesus' saying and doing as the Messiah for Israel.
About Judas from the beginning Jesus was prophesying evil things of him, and even in a prayer to the FATHER that sadly he had to be lost.
For the scripture declares, satan entered into Judas, as how satan in the future enters into anti-Christ.
Both happen to be normal men, but inwardly satan is at work through them, since the truth and the things of GOD never in them.
Why did Jesus on the Cross prayed to the FATHER, 'Forgive them, they knew not what they do.'?
Because as Jesus said, 'The god of this world have blinded the minds of unbelievers.'
Shalom in the name of Jesus Christ