Most heartbreaking part of Dean's dilemma

• Asking Castiel if serving the angels will save Sam, and Castiel replying 'If it give you comfort to see it that way'

• Dean and Bobby listening to Sam's screams from the detox chamber

• Real Dean: 'I guess I found my line. I won't let my brother turn into a monster.' Fake Dean: 'Monster! Sam, you're a monster!'

• Dean refusing to think of giving Sam demon blood, even if withdrawal will kill him: 'At least he'll die human!'

• 'You walk out that door, don't you ever come back!'

• Dean saying exactly the wrong thing at the wrong time to push Sam's buttons and drive them apart.