7. Becoming An Enemy
BBC This was touched upon in Asylum of The Daleks with the reveal that Oswin had been converted into a Dalek, but the Doctors companion being his enemy is another rarely used concept that could have the potential to be a very strong ending for Clara. Although Claras been shown to have the willpower to overcome mind control before, depending on the enemy and manner of control, theres nothing to say that she cant end up being completely controlled. Especially since the Cybermen are returning in the Series 8 finale and very few characters have been shown to overcome Cyber-control. Clara struggling to overcome Cyber-conversion and either sacrificing herself or getting the Doctor to kill her as an act of mercy (à la Kamelion in 1984s Planet Of Fire) would be an absolutely heartbreaking ending for her. Not to mention a welcome change of pace to the endings of previous New Who companions which are always bittersweet at their very worst.