the Cardassians maybe. Almost certainly the Ekosians, but they don't really count because their culture is based on Earth Nazis
The Klingons have Rura Penthe, where convicted "enemies of the Empire" were sent to mine dilithium
The Bajorans were executed in large numbers during the Cardassian Occupation. In addition to these executions thousands and thousands of Bajorans were put in brutal work camps
The Remans suffer in their planets dilithium mines under the cruel eyes of the Romulan people. The Romulans have chosen the naturally nocturnal inhabitants of their capital world's planetary twin to slave away in the planet's dark mines. The Remans are openly declared as slaves by the Romulan Empire despite the overwhelming contempt almost ever major interstellar power have for such practices.
There is a distinction here between death camps and slave labor camps
"Gallitep", as it is described in the Star Trek: Deep Space Nine episode "Duet", is a "forced labour camp". The undertone of Cardassians as genocidists runs through both Star Trek: The Next Generation and Star Trek: Deep Space Nine. The Gul Darhe'el subplot is certainly an allegory on war crimes. ProfessorTrek 20:47, July 16, 2011 (UTC)