Repentance is synonymous with remorse.
Matthew 27:3 Then Judas, which betrayed him, when he saw that he was condemned, repented himself, and brought back the thirty pieces of silver to the chief priests and elders,
Jesus said, from the cross, father forgive them for they know not what they do. I believe Judas was forgiven in that instant and with his repentance for his betrayal, he was forgiven his act.
However, something that we can't ignore is this.
In the upper room if we read Luke 22 we may presume Judas received what we call communion, along with the other disciples.
Further, Jesus knew what Judas was going to do. He told him to go and do what he had to do, and do it quickly. But, and this is easily missed if we don't read carefully. Satan entered Judas when Jesus gave Judas the morsel of bread that was the symbolic flesh of Jesus.
And knowing this as he would, Jesus then told what would be Satan that had possessed the body of Judas, So Jesus told him, "Hurry! Do what you have to do."
Therein is the issue. It wasn't Judas who went forth, at Jesus' insistence, and betrayed him to the Sadducees of the temple. It was Satan.
And really, that makes sense. Jesus was born to give his life to seal the new covenant. Jesus was to die so to remove Satan's power over death. Therein, Satan, who before has operated as we know according to God's plan (Job), would be the one who would happily turn over the one he'd tried to tempt to obey him, to those who wanted him dead.
Because Jesus' Disciples wouldn't betray Jesus to his enemies. But Satan would be the perfect one to do that and to those very one's Jesus called the Pharisees who thought to call him to account for his actions on Sabbath day, of belonging to their father the Devil. John 8.
This then helps to make sense of Judas' remorse, repentance, once he realized what he'd done. He didn't do it.
But it was done and Jesus was in custody. Which would explain how he felt remorse, returned the silver, and hanged himself. Because the law said, cursed is anyone who hangs on a tree. Matthew 27.
And that curse is also why Jesus was to die on a tree, the cross, to take the sins of the world upon himself.
Jesus had to die on a cross, tree, to fulfill the plan of God. No Disciple would betray him. Of course Satan would have to be the one to occupy the body of a Disciple and do the deed. But Satan wouldn't have known God's plan. He's not going to do something that is going to insure he loses his power over death being he was, and is, lord of this world. John 12:31
And how else, if not for Satan, would Jesus have been killed per God's plan but also unbeknownst to them, that of the Pharisees?
We're not responsible for what Satan does if he occupies our body, possesses us. Why would Judas be any different? Especially when it can't really be called a betrayal, when Jesus, knowing his purpose, told "Judas" to go and do what Jesus knew he had to do. And quickly.
Judas had remorse when he realized what had happened. I believe he was forgiven by Jesus from the cross. Because Jesus knew Satan was within Judas. That's how we know this through the scriptures. And that especially reiterates Jesus words of forgiveness from the cross. "Forgive them for they know not what they do." That was Judas to a T. Satan was in him. Judas didn't know what Satan was doing. That's why the scripture tells us, when Judas realized what he'd done....He didn't realize it while doing it. He realized it when he saw Jesus in the custody of the Pharisee's and Sadducees who wanted him dead.
Satan was the son of perdition. JOHN 17:12 “While I was with them in the world, I kept them in Your name. Those whom You gave Me I have kept; and none of them is lost except the son of perdition, that the Scripture might be fulfilled.
Some think Judas is that son of Perdition. But as we know, Satan, who can do nothing without God's permission, was within Judas. He is the one that is lost. Not Judas.