Star Trek: 10 Starfleet Officers Who Betrayed The Federation
9. Michael Jonas
This guy. This goddamn guy.
Michael Jonas joined the crew of the USS Voyager when he was stranded in the Delta Quadrant, along with the rest of Chakotay's cell. While he seemed to adapt to life in Starfleet, he did in fact openly object to the way things were run by Captain Janeway. Sensing that he might be able to take advantage of this, he secretly contacted the Kazon.
He was exposed after something of a sting operation involving Tom Paris, Captain Janeway and Tuvok - but with a little help from Neelix. Jonas had made the big jump from selling secrets to out and out sabotage, shutting down systems with the hope of forcing the ship to land. Once landed, the Kazon would then attack.
Paris discovered what Jonas was up to, but to do that, he had to leave the ship. The meant that he couldn't let the crew know in time. However, Neelix came to the same conclusion and was in a position to act. After a brief fight, Jonas was thrown into a plasma stream, killing him instantly.