Shuma-GorathEditShuma-Gorath is a Doctor Strange Villain, whose powers include transdimensional control, virtual omnipotence, and the ability to assume kinky tentacle form. Clearly these align with The Rani's abilities. Furthermore, Shuma-Gorath is one of the few Doctor Strange villains who has managed to actually kill the Doctor, albeit indirectly. The Rani likewise manages to pull off this feat.
Doctor Strange = The 0th Doctor?Edit
The link becomes even more apparently evident when we compare the two characters to which Shuma, and The Rani act as villainous foils to.
Doctor Strange is an ageless, mythical eccentric who was originally created in 1963. The Doctor is similarly an eccentric who debuted in 1963. Both Doctor Strange, and The Doctor use non-conventional methods to defeat their adversaries. In Strange's case magic and in the Doctor's case magic.
It can be concluded therefore that since Doctor Strange and The Doctor are more or less one in the same, that the most intimidating Doctor Strange villain of them all must also be the most intimidating Doctor Who villain of them all. Therefore, we can see that Shuma-Gorath is a timelord, the only truly intimidating Doctor Who villain; and due to his tentacly visage we can only assume that that villain is The Rani.