Star Trek films are defined by a variety of elements, but maybe none more important (other than the plot) than the villain. A good villain makes a good story great and a bad story memorable. A good villain who can play off the hero(s) is key for a show or a film to stand out, and it's just as important for Star Trek. The films with the best villains are the ones at the top of the mountain.
Wrath of Khan, Undiscovered Country, First Contact, and Star Trek 2009 all shine due to the fact that the villain is well-written, properly motivated and the actor behind the role delivers a strong performance. While some fans didn't like Benedict Cumberbatch's portrayal of Khan Noonien Singh during Into Darkness, he did deliver a very good performance, that is still highly quotable to thi this day.
So with Star Trek 4 in development, we hope, we're looking at what classic Original Series characters we'd like to see reimagined for the fourth and possibly final Star Trek Kelvin film.
Dr. Roger Koby
Maybe the most on-the-nose suggestion today is Dr. Roger Koby. The villain from the original series was heavily involved in robotics and artificial intelligence. With the rise of AI and the concerns around it, Koby could be the perfect stand-in for some real-world issues.
General Chang
While everyone loved Khan in the second Star Trek film, General Chang from the sixth film is as good as a villain as anyone. Christopher Plummer brought him with such energy and style. His cadence, bravado, and cunning were all on full display as he backstabbed and betrayed his own people just for a shot at glory and power. Modern politics is getting out of hand, watching Chang murder his way to power would put a spotlight on the problems we're currently witnessing.
Gary Mitchell
I just think it'd be cool if Gary Mitchell started throwing everyone around with his telekinesis all movie. Star Trek films rarely, if ever, look at beings as powerful as Mitchell. At least, not at ones who stand as a direct threat from the start of the film to the end. This long-forgotten character could be a massive asset for the fourth film.