Star Trek: 10 Underrated Villains
6. The Breen
Different Star Trek series have tried to bring new aggressive races in over the years. Klingons had become allies, and producers worried that standards like the Romulans were boring to fans. The Borg and the Cardassians were two very successful attempts though other races like the Breen never quite seemed to click.
A warlike race, the Breen took being secretive to a new level. Their home planet was reputedly incredibly cold, so any Breen that ventured away from it wore a refrigeration suit. Supposedly, no one outside of the Breen had ever seen one of them without a suit on. While they popped up in other series, their biggest contribution was to Deep Space Nine when they joined the Dominion/Cardassian alliance.
The Breen never really caught on with fans, though they probably should have. They were a race of warriors with incredible engineering skills. They developed an energy dampening weapon that almost won the war for the Dominion. Their inclusion in that story as the new Alpha Quadrant favorites of the Founders was an important element of the ongoing war.