4. Phage-less Vidiians - Lifesigns (Voyager)
No disrespect to the Polite Klingons aka the Kazon but these were Voyager's first truly interesting aliens with a chilling twist in their tale. The makeup was great, the concept of organ harvesting to try and hold the all-consuming nature of the Phage at bay was a spark of early genius for the stranded starship story. There was genuine terror, moments of shock and even the odd blowing up of Voyager into the bargain when these aliens showed up in the vicinity. Then in the second season they dropped the ball, nay the bomb with the heart-to-heart bad-guy-is-our-friend story. What could have been such a drastic makeup change and have unveiled some cool alien bumps and lumps was nothing more than a nicely smoothed and polished forehead. When the Phage was iradicated they were just average humanoids with very little to make them visually interesting. There wasn't even a cranial ridge in sight to peak some interest. In some respects their unveiling was one of Voyager's biggest disappointments and the Vidiians quickly faded from view after this shocker.
Reminds us of: Missed Opportunities