So I was reading one website attacking Eternal Security suggesting that the way Eternal Security believers use part of John 17:12 "I have kept, and none of them is lost" as being undermined by the following statement in regard to Judas.
First of all, they horribly misrepresent the passage by saying "Jesus admits to losing Judas". This passage is not an admission of any failure. "I kept them in thy name: those that thou gavest me I have kept, and none of them
is lost, but the son of perdition; that the scripture might be fulfilled." This is presented as the absolute only exception, the exception that proves the rule. We this absolute only one exception principle elsewhere in Scripture, the Blasphemy against the Holy Spirit is the only Sin that won't be forgiven.
The reason Judas is allowed to be Lost is to fulfill Bible Prophecy. Psalm 19 and Zachariah 11, the Idol Sheppard that Leaves the Flock. There are no Bible Prophecies about Salvation being lost. Jesus said to the damned in Matthew 7 (even specifically proffering Christians who are damned) he NEVER knew them. There is no such state of a damned former believer.
Scholars may debate all day if Judas was really Saved and lost it, or just rhetorically being spoken of as if he was one of them (I prefer the latter view). But either way the point is he's one of a Kind. Son of Perdition is a Unique title used only once elsewhere in Scripture, where I believe it's The False Prophet. And still the same person as Judas.