There is a fine difference between “repent” and “regret”. I can’t recall where I read this recently, but the main thrust of the argument about “regret” was that “regret” was an egotistical kind of sorrow; more based on how the person’s sense of him/herself as a “good” person is compromised by a particular wrong thought or action, which the person then “regrets”. . .
As opposed to “repent”, which is a humble acknowledgement of error, has nothing to do with the person’s self but everything to do with the person feeling sorrow and contrition over the wrong he or she has done to God. Finally, a person who feels repentence always tries (so far as he or she is able) to ATONE for the sin. A person who “regrets” something quite often never does more than “moan” about HIS regrets, but never does much of anything to make up for them, often feeling that the actions can’t be forgiven, and sinking into depression and even committing suicide from the “regret”. . .
So Judas may have regretted his sin, but he doesn’t appear to have repented for it.
Peter, OTOH, repented his sin. He knew himself (“Depart from me, Lord, for I am a sinful man” was one of his speeches to Jesus), he knew what he had done and he did his best to atone for it, do the right thing, and help others.
Just my :twocents: