Alien Conquistadors

Basically I'm looking for media where the world is invaded by aliens who want to Civilize humanity. They tell us they're here to save our souls, but what that winds up meaning is slave labor, forced conversions, torture, and executions. Bonus points if it covers Earth's later status as a colony to Space-Spain, and more bonus points if this is all tied to the Space-Doctrine of Discovery uniting Space-Europe under the Space-Pope

I know there have to be a few popular stories out there with premises like this, but I can't think of any, and I'd like to try some