Also, when Dean listens to Jack's soul-rejuvenating revelation of unintentionally killing Mary, he actually listens and forgives "the kid." This is Dean's way of quietly redeeming himself for the times when he constantly doubted Jack's entire presentation, and overall just didn't trust him.
When Jack killed Mary Winchester, he sought to redeem himself by creating new angels but it didn't help and he was locked away by the Winchesters. Jack escaped and roamed Earth before he was confronted by the Winchesters who intended to kill him but stopped.
