The middle of the pack of Star Trek's villains are the ones who aren't all that bad but are flawed enough in their own right to not be too great, either. They're the ones who had the potential to be great but just couldn't quite get there. The order is fairly interchangeable, depending on how you feel about a certain villain at the time.
6. Kruge / Christopher Lloyd / Star Trek III: The Search for Spock
5. Shinzon / Tom Hardy / Star Trek: Nemesis
4. Nero / Eric Bana / Star Trek (2009)