2. The Rani
Just like the Doctor and the Master, the Rani is a Time Lord outcast and would certainly make for an interesting villain in the new series. A renegade Time Lady, she has no love for Earth and is completely amoral, focusing entirely on getting her experiments finished. Similarly, she does not care for the casualties that she causes as she considers humans as beneath her. Unlike the Master however, she has no interest in world domination but is simply interested in her own agenda. The Rani was first introduced late in Doctor Whos original run, appearing as the villain in notorious episodes such as Dimensions in Time. During that episode she travelled around the universe and time trying to imprison the Doctors first seven incarnations. Now, interestingly she was hinted to have had a relationship with the Doctor at some point in time, which sounds rather like Missy from the latest series. Also, given the fact that the Time Lords are around somewhere, its easy to imagine that she is also waiting someplace, plotting and scheming, and it seems a perfect time to introduce her given the Master isnt appearing any time soon. Sadly, back in 2012 Steven Moffat said he had no reason to bring her back, but that could easily be a diversion, and frankly she deserves her due in a real high quality story.