10. Ru'afo - Star Trek: Insurrection
Ru'afo was a fine villain. He wasn't anything special but he had personal ties to the characters in the film. He was selfish and disregarded life for his own desires. He was a throwback villain to the 1960s but sadly he was too one-dimensional of a villain to stand out against the waves of better characters to come.
9. Krall - Star Trek: Beyond
You have Idris Elba and you stick him in a character where you can barely tell it's Idris Elba? What? What are we doing here? The over-the-top prosthetics and the desire to have one of Starfleet's own being the core villain severely conflicted against one another. Had Elba just been a human who was 'lost' in the same area where the movie took place, only to reveal his plans to destroy the Federation by using the Enterprise, that would've been a better story. Instead, Elba was reduced to a monster-of character and in doing so was robbed of all of his charisma.
8. Shinzon - Star Trek: Nemesis
Played by Tom Hardy, Shinzon isn't a well-written character, but everything else lands. He's able to gain a level of control against the Romulans, while also bringing in a third part of the Vulcan/Romulan family, with the not often mentioned Reemans. He also became a large enough threat that his actions led to the death of Data. not a great character, but we're starting to turn the corner.