There is only the Tau Empire!
For those unfamiliar, the post's title comes from the tagline for Games Workshop's miniatures wargame, Warhammer 40K. Originally a sci-fi version of their Warhammer Fantasy Battles line, 40K has since moved away from being nothing more than elves with grav-tanks and orcs with machine guns, opening up its universe and coming more fully into its own. The game is as expensive as it is time consuming, but fortunately it's also as much fun.
For myself, despite initial forays into the Tyranids (the inspiration for the Starcraft Zerg) and the Imperial Guard (WWI armies with lasers and psykers), it wasn't until the introduction of the Tau Empire that I really got into the game. Although it probably helped that their introduction roughly coincided with me getting my first decent job, and therefore having enough money to actually build a decent army. And yes, that means I did try to play the horde-based Tyranids and IG on a shoestring budget.
The universe of 40K is a world that Thomas Hobbes would recognise in a second; life there is nasty, brutish and, quite frequently, short. To give a sense of the mood, the Tau Empire is a totalitarian caste-based system, ruled by a group who command unnatural loyalty from all those around them, dedicated to the conquest of the galaxy and the extermination of any races incapable of submitting to their rule. They've been accused of practicing mind control-based slavery with the insectoid Vespid, and even of sterilizing whole human populations on rebellious worlds.
But because they actually give you the choice of surrendering before they shoot you in the face, they're as close to 'good' as this setting gets!