SuperWho AU! where the Doctor says goodbye to the Winchesters.
"There were more than 900 years losing people that I care and love… I think it’s time to stop creating hope that one day things will be different. I’ll always lose everything around me and it is time to face my destiny and be alone. So I came to say goodbye, fellas. Please take care and avoid getting into trouble. You are young, too young, and still have a chance to change things… So please, don’t waste this chance. It’s more precious than it looks. So that’s it… Goodbye, Winchester boys.”