"And that thief did nothing more than believe. He said, 'Remember me when you come into Your kingdom.'"
Au contraire: that rebel was hanging there for hours and hours and hours enduring some of the most hideous torture that the human mind has ever devised. Jesus was experiencing it too.
AND he respected Jesus' second commandment, telling his colleague in crime to shut up and leave the poor innocent Jesus alone.
AND he respected Jesus' first commandment, simply, by believing.
So, there was the expression of faith, and of compassion, both of which were redemptive.
The extent to which the man's long suffering on his own cross, to die of broken legs and suffocation, was the purgatorial balloon payment on his sins we won't know until we die and ask the question, if we care at that point.
Romans 10:13 - Whosoever shall call on the name of the Lord shall be saved.
That's the important, and scriptural, part of your post.