She's only appeared in two full episodes to date (Series 8's Dark Water/Death in Heaven finale) but she has already firmly established herself as a force to be reckoned with. Suffice to say, you wouldn't want to meet this renegade Time Lord in a dark alley. She'd sing "Oh Missy you're so fine" and then obliterate you on sight. After taking a selfie with you, of course. Speaking of which...