9. The Master In "Castrovalva"
As a fellow Time Lord, the Master has powers at least equal, if not superior, to the Doctor, and has been responsible for countless almost-successful attempts to conquer Earth. He also has a nasty habit of coldly murdering anyone who happened to stand in the way of his plan. That's why it was baffling in "Castrovalva", Peter Davison's initial outing, that the Master spends the majority of the story disguised as a silly old man in an incredibly stupid hat. What makes it worse is that his so-called evil scheme consists mainly of strapping the unfortunate Adric to a rather large bondage device (yikes!). Just a couple of episodes ago, the Master was inches away from causing the entropy death of the entire Universe. Now he's a fussy little white-bearded gnome who looks like he wandered out of a Tolkien novel, calmly chattering with the rightfully confused Doctor. You'd think the Master would take advantage of the Doctor's weakened post-regenerative state to finish him off once and for all, but he does everything short of offering him chicken noodle soup and a warm bath. Their future meetings, thankfully, would prove to be somewhat less amicable.