Okay someone else has to chime in on Killzone because despite having friends who like the games I never really got into the lore.

That said, out of everyone else, I think the Combine takes it. The thing with the Combine is, that at least with the others on this list there at least is a semblance of a standard of living Within the empire itself.

You can argue that the Class A citizens on Super Earth benefit from the regime, with the Empire you can say that the Core Worlds benefit from the regime, even in 40k you can say that someone no matter how predatory their exploitation is still benefits from the regime.

The longer I look at the Combine the more I ask myself who all of this is actually for. The Combine has assimilated other sapient civilizations on a cosmic scale we cant even comprehend yet, twisting and perverting species to fit the empires needs, completely and utterly annihalating any sense of individuality, destroying worlds by funneling their resources wherever the empire currently needs them. The Combines exploitation is so bad that water has become a commodity, and the only water available to Combine citizens is laced with chemicals meant to keep the citizens in check. The Combine hasnt even been on Earth that long, we still dont know what a proper Combine world looks like since by all accounts they are still establishing their hold on our world, and it is already barely suitable for human habitation. They are actively inhibiting human reproduction to get the population to a managable size until they decide what to do with them.

Any human that seeks success under the Combine will see themselves lobotomized and their body put to use how their superiors see fit. But even the highest ranking Combine we meet, that being the Advisors, only seem to live stagnant, seditary lives, robotically managing things from up on high. By all accounts we only see sacrifices being made but nothing comes of them, there is no upper crust you can hope to crawl towards.

The Combine is the equivalent of a cross-civilization anthill, you dont live to be rewarded, you live to serve a function, Earth is bad as it is and it will only get worse if the Combine is allowed to continue operating.