Disclaimer: I don't own them…
Two angels were holding Sam captive as Dean stood before Michael.
"You promise that you'll look after Sammy, if I say yes?" Dean asked.
"Of course, Dean, I give you my word." Michael's deep voice replied from above.
With one last look at a struggling Sam, Dean whispered "I love you, Sammy" and nodded his consent to the heavens.
"NO! DEAN!" Sam screamed as a bright light engulfed Dean causing Sam to turn his head away to protect his eyes.
As the light died down, Michael/Dean walked up to Sam. "I made a promise to my vessel that I would take care of you." He gently ran his hand through Sam's brown hair, pulling Sam's face towards him.
"I promise you that I'll keep you safe from Lucifer." He continued as tears streamed freely down Sam's face.
"Please NO, don't! Just give Dean back to me." Sam yelled trying to break free of the angels' hold on him.
"Hush, Samuel. Everything is going to be alright." Michael/Dean said as he placed his hands on Sam's neck.
Then he snapped Sam's neck.
With a sigh, Michael/Dean bent to pick up Sam cradling him in his arms. With a nod to the two waiting angels, he carried Sam to awaiting pyre where he lay him down and lovingly arranged Sam's clothes while the two angels brought gasoline and fire to light the pyre.
As the fire consumed Sam's corpse, Michael/Dean gazed at it as a bright light from the sky illuminated the pyre. Sam's spirit rose up from the fire and floated up toward the light.
At least now, when the battle is over, my vessel will get to be in the heavens with his brother for all eternity, together again in peace and safety. Michael thought to himself with a satisfied nod as he turned away from the burning pyre and headed to battle Lucifer.