I’d say Coruscant from Star Wars, as that would give them a wider area of control over the Galaxy and the outer rim. I’d probably also say New Genesis/Apokalips from DC, but they’d most likely fail due to the New Gods being way larger and more powerful than them, with the average New God being about the size of a star with them adjusting their size via boom tube. I’d probably also say Titan from Marvel, as the Eternals are incredibly powerful and would be able to intermix with humans, making them perfect for Viltrumite take over