10 MORE Star Trek Villains Who Killed The Most
8. Crell Moset
Crell Moset was introduced in the episode Nothing Human. He was a Cardassian scientist, appearing on the USS Voyager in the form of a hologram, created to assist the EMH. His affable, charming manner belied a dreadful secret: Moset was to the Bajorans what Mengele was to the Jews - a monster, through and through.
Moset had done most of his research during the occupation, using Bajoran slaves as his own private test subjects. He conducted inhumane experiments, killing thousands in the pursuit of, as he saw it, scientific advancement. Though the outcome of his research allowed the EMH to save both Torres', and an alien parasite that had attached itself to her, lives, the cost of this knowledge was simply too high.
The former Maquis members of the crew would have nothing to do with this hologram, and the EMH's own conscience couldn't allow for the continued use of this research, knowing how it had been achieved. Moset, who was very probably still alive in the Alpha Quadrant at this point, received a small form of just deserts when his research, and the hologram used to embody it, was deleted from the ship's database.