4. Garth of Izar (Whom Gods Destroy - The Original Series)
I'm personally still gutted that Garth didn't turn out to be the main villain in Star Trek Into Darkness; I think Cumberbatch would have done a cracking job of taking on this part! So, former captain Garth, a man two dilithium crystals short of a warp core with an entourage that would make Miley Cyrus blush. Add to that his ability to shapeshift and you have one interesting villain at hand here. Off-screen he's come back from the brink of death and then managed to wipe out an entire species, which isn't a good career move. His time at the Elba II asylum twists him even more with his hopes of escape lying in his ability to work out the code answer that Kirk has laid out with Scotty before leaving the Enterprise. Exceptionally clever Despite being a little less level-headed, Garth could probably have rivalled Khan for intellect and it might even be the case that had he returned for another chance to get off Elba II. If this had happened, the character would have become darker and a good, sinister major villain. In Whom Gods Destroy those that follow Garth are just as important however expendable they might be to his long term goals as the Orion girl Marta finds out. He really does give everything a shot to try and deceive Scotty, yet trying to beat Kirk the man who beat the No-Win Scenario is probably as easy as shooting fish in the proverbial barrel. Ultimately he's left in a "Could be back" state once defeated. Heavily sedated, he might one day recover to be something of the man that Kirk revered, but that's for another day.