It never occurred to you that the thief's suffering, shared with Christ, may have very well been his purification?
No...actually it didn't. Because the purification to which you refer was accomplished when his sins were forgiven him by the crucifixion of Christ... the thief could not do ANYTHING on his own to add to his "purification." To imply that would be to imply that the death of Christ was insufficient!
"13 And you, who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, 14 by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross. 15 He disarmed the rulers and authorities and put them to open shame, by triumphing over them in him.
(Colossians 2:13-15 ESV)"
What can a dead person do for their own salvation? Apparently nothing. What did Christ's death do? EVERYTHING.
Hoss