Dean wouldn't remember it, Castiel knew. The righteous man remembered hell, of course; he remembered every second of that bottomless despair. But he didn't remember being pulled out.
Castiel had been surprised when he was instructed to retrieve a soul from Hell and restore it into its vessel. But back then, he wasn't an angel to question orders. Castiel had descended to the pits of hell, flown through the decay and blood, listened, detached, to the screams. The demons hadn't dared touch him; he had been lent extra strength for his assignment, and resonated angelic power.
Dean was there, in the depths, a cruel blade held in one hand, standing before the bloodied body of a girl bound between wooden beams. She was sobbing head bowed, voice raspy from her screams. Dean dropped the knife and took the girl's head in one hand. She cringed away, but had nowhere to turn. Dean murmured something, too soft for anyone but the girl to hear, and she opened her eyes wide, tears streaming freely.
Castiel reached for the man then, closed a hand over his upper arm, and began ascent. Touching Dean's soul was painful. Castiel could feel everything, everything that the man had experienced, every emotion, every gash and hole and scar that composed his beaten soul. He felt a rough, stone-like exterior that had been built up over the last forty years. Beneath that, he felt the raw, flayed, broken core that was Dean Winchester.
Dean thrashed violently, writhing in the angel's grasp until he had turned and could see Castiel properly, for the blinding light and energy and intention that he was. Dean's eyes widened. Castiel felt the exterior soften and begin to crack.
Slowly, Dean lowered his head and and his hands clutched desperately to the presence of Castiel, and he cried as his soul crumbled.
"I'm sorry, I'm so sorry," he sobbed. "So sorry,"
He stretched a hand upward, clawing at Castiel, desperate for the light after a millennium of darkness. Castiel hesitated before lowering the hand that wasn't holding fast to Dean's arm. Dean took it and kissed it and buried his face in the brightness and cried. Castiel felt, at the very depths of Dean's soul, something that so many years of hell should have destroyed.
A tiny, barely tangible, flickering glimmer of innocence, of love, of genuine, innate goodness that had no place somewhere this dark. He felt the words that Dean had spoken to the girl and to every soul that he had tortured in his endless years in Hell; words that had soothed their broken beings, and advice that Dean would never, never be able to take for himself.
"Forgive."