“For the Uniform” is episode thirteen of season five of Star Trek: Deep Space Nine.
Sisko is visiting a refugee camp on a planet in the Badlands. He has a meeting with an informant who has information on Eddington, the Starfleet officer who deserted and joined the Maquis in “For the Cause”.
The informant doesn’t turn up, but Eddington does instead. The latter has marooned the former on a rather unpleasant planet, and uses the opportunity to berate Sisko. When Eddington teleports out to his ship, the Defiant pursues, but the traitor had left a virus embedded in the ship that utterly cripples it. Eddington’s own ship fires a few shots at the helpless Defiant, but doesn’t destroy it.
When Sisko gets back to the station, he is informed that Starfleet has taken him off the case and put the captain of another ship in charge. Sisko takes Eddington’s betrayal very personally and, when the still-damaged Defiant turns out to be the only ship that can get to Eddington in time, he takes it out. Eddington is making Cardassian planets uninhabitable for that species in the Demilitarised Zone, and has managed to cripple the other starship sent after him.
Eddington’s attacks have ramped up, and he is constantly taunting Sisko (using a newly installed holo communicator). So the latter comes up with a way of defeating him, one in the role which Eddington considers him to be.