This is how I understand the Judas topic.
He was His, the Father gave Him, but He was an EXCEPTION. He allowed the devil to enter Him to fulfill scripture.
While I was with them, I was keeping them in Your name which You have given Me; and I guarded them and not one of them perished but the son of perdition, so that the Scripture would be fulfilled.
John 17:12 NASB
Why Judas? We can speculate on that but I haven't seen, yet, any reason other than to fulfill scripture. Perhaps, it was because of His heart condition, but that is unknown. It says, that at the passover satan went into Him, not before, that He belonged to Him.
Now the Feast of Unleavened Bread, which is called the Passover, was approaching. The chief priests and the scribes were seeking how they might put Him to death; for they were afraid of the people. And Satan entered into Judas who was called Iscariot, belonging to the number of the twelve.
Luke 22:1-3 NASB
Now was He always the Son of perdition and that is why Satan entered Him? I don't know, maybe you all can show me scripture. Did He repent, it appears great lamenting and regret occurred.
But we see that He says He perished. I want it to be forgiven because he felt horrible (which he should've but he was merely fulfilling scripture) I am not the decider of such things, and just because Satan entered Him at the point of betrayal doesn't mean... wait... He says something pretty pivotal here...
Jesus answered, "You would have no authority over Me, unless it had been given you from above; for this reason he who delivered Me to you has the greater sin."
John 19:11 NASB
Everything points to Him having remorse but in that scripture John 17:12 we see He perished so the scripture could be fulfilled. Now does He mean Judas perished his earthly life. He did say while I was here.... and none other died before His crucifixion. I don't know, though, it says whoever believes me, will not perish. So I think the word choice being the same, He was speaking spiritual perish.
Speculation city going on. We know He (the Father) gave Judas. Scripture says that but to fulfill scripture satan entered, thus given over, now He was the son of perdition.
We can not use Judas as an example because he was an EXCEPTION and we can not question if it seems unfair because we know God is good and that He knows what He is doing. He shows mercy on who he chooses, doesn't mean He is cruel and selective for no reason. He knows the hearts of us but it seems in the case of Judas it was again to fulfill scripture.