Return to Greatness

Sombra is back, but not in the way anypony thought. Found dying on a mare's front porch, he is taken to a hospital. He arrived too late however, and is in a coma. Twilight Sparkle asks if she could reform him, like for Discord. Celestia agrees. What will happen when he wakes from the coma? Can he be reformed, or will he have to much darkness remaining in his heart?