What would be the most realistic way for WWE creative to turn Cena heel so that it makes sense?
I would have CM Punk, being the cult leader and master manipulator, play mind games on Cena until he finally gives in and goes to the 'dark' side. He tells Cena that he's only great because he has the fans support, and that he'd be nothing without them. He says the kids that love him now will grow up one day and turn on him. It doesn't bother Cena at first, but after awhile the frustration kicks in and it allows for a smooth, gradual turn rather than a sudden one.
I would have CM Punk, being the cult leader and master manipulator, play mind games on Cena until he finally gives in and goes to the 'dark' side. He tells Cena that he's only great because he has the fans support, and that he'd be nothing without them. He says the kids that love him now will grow up one day and turn on him. It doesn't bother Cena at first, but after awhile the frustration kicks in and it allows for a smooth, gradual turn rather than a sudden one.