A great plot means a great conflict. A great conflict usually means a great villain. For me, it seems that the better episodes of TOS had a lot to do with how compelling the villain was. Here are my top 5 best and worst TOS villains: Best: 5. Redjac 4. Gov. Kor 3. Doomsday Machine 2. Romulan Commander (BOT) 1. Khan Worst (5 = least bad or most tolerable, 1 = please die now): 5. The Earps 4. The Gorn 3. Romulan Commander (TEI) 2. The Providers 1. Gorgon I left out characters like Mudd, Cyrano Jones, the Squire, and Charlie X (all of whom I thought were great) because I have trouble classifying them as "villains." I see them more as nuisances that Kirk and company had to overcome as opposed to forces that intentionally sought to antagonize them out of pure malice and/or political reasons. How about your list?