10 Doctor Who Villains Who Ultimately Turned Good

9. Lady Cassandra

By far the most devious trampoline in the entire universe, Lady Cassandra was nothing more than a piece of skin held in place by a metal frame, a result of the countless surgical procedures she had undergone in order to extend her life.

She was egotistical and self-motivated, prioritising her lifespan and her looks above everyone - and everything - else. But, eventually, she did learn to care for others.

Cassandra first encountered the Doctor in the Series 1 episode The End of the World, where she tried to kill the guests onboard a space station, purely for financial gain. However, this plan didn't work out, and the Doctor left her skin to dry out and explode amidst the scorching heat of the sun. Even Factor 50 wouldn't have saved her.

But her brain managed to survive this incident, allowing her to live on. In Series 2's New Earth, Cassandra was trying to transfer her consciousness into a human body, determined to live normally once again - y'know, with arms and legs and stuff.

While she did succeed in doing this for a short period of time (in an extremely funny sequence, she enters the bodies of both the Doctor and Rose) she eventually stopped trying and accepted that it was time for her to die. This change of heart was brought on after she took over the body of an infected person and felt that person's pain, prompting her - in a rare act of kindness - to help the Doctor cure an infected army.

Cassandra then entered the body of her servant, Chip, but he was too weak, and his body fizzled out with Cassandra's consciousness held inside.