2. Nobody No-One
The premise behind Nobody No-One is genius in and of itself. No-One is a Word Lord, a mirror of a Time Lord but taken from a place 45 billion dimensions to the left of the Doctors own. His power is taken from words, rhymes and literature, and made for an excellent premise. Apparently, the guys power was just endless, as long as you could turn it into words. By saying things like Nobody could turn off the sun, No-One could do exactly that, meaning the whole thing would take on a twist not unlike when the Tenth Doctor met Shakespeare or the whole insanely bonkers Dr. Moon premise in Silence in the Library/Forest of the Dead. However, its the sort of insanity a showrunner like Moffat would do well with, full of novel twists and turns. Almost fittingly, hes only ever existed in audio form, fighting the Seventh Doctor in The Word Lord and A Death In The Family. This perhaps gives him an advantage over any other villain on this list entirely because powers aside, hes almost a complete blank slate. Remembering that the show does well when it attempts to put a spin on a Timelord see Amys Choices Dream Lord for a reference seeing something as unique as this would be an incredible watch with any Doctor, never mind Capaldi.