In Warhammer 40000, the Tau were created to basically be this trope, and whilst some Fan Dumb has forced them to get darker since their introduction, they still manage to be this. It says a lot about the state of the 40k verse where the race with a "communist manifest destiny" motif, who openly admit to wanting to conquer the universe and make all other races part of their empire, who resort to violence if their efforts to diplomatically subsume other planets fail, and who (in one videogame comment of dubious canonicity) are implied to set up concentration camps and forced sterilization programs for races that resist their conquests and fail, are still the comparatively good guys.

Is there any proof of Word of God sort? Or is it some other fandom being funny and habitually exercising internet-telepathy? Because "a faction modeled after the RL factions infamous for their invariable predilection for mass executions and building concentration camps was introduced into Grimdark, and surely it was intended to be BETTER than the originals" is a thesis that needs some solid support. And possibly lots of sealant, to hold water.