10 Best Battles In Star Trek's History
7. Second Battle Of Chin'toka
Season 7, Episode 20 - The Changing Face of Evil
The only time in Star Trek's television history that a hero ship was permanently destroyed on screen.
The arrival of the Breen into the Dominion War arc handed the Federation and its allies one of the most decisive losses in their entire history, with the USS Defiant one of the 300+ ships destroyed in the conflict. For context, Wolf 359 cost them around 40.
In terms of actual screentime, it's relatively light compared to other entries in this list, but for the pure stunned silence it sent fans into it's gone down in Trek folklore. The Defiant, presented as one of the toughest ships in the history of the franchise, given a solid back-hander from one blast of the Breen's energy weapon, and then blown to pieces mere moments later.
The visual of it floating in space, flanked by all number of flaming wreckages of both Romulan and Klingon persuasion, brought a sense of peril to the Dominion War that no other Star Trek series arc had ever really had before. We'd seen Starfleet bleed before, but never at the cost of the show's own ships.