In my current Stellaris game, I've nerve stapled all races in my empire besides my own, and gene-modded them to be delicious (no, really that's an actual trait) aside. This allows me to grow other species as livestock, which in turn means I can build more power plants and mines instead of farms. Now, I'm playing a megacorporation, and have branch offices of my corporation in the space of every other empire in the game except for the genocidal robots, who I'm in the process of exterminating from the face of the galaxy. Despite the fact the other empires pretty much all hate me for being xenophagic, they're so weak compared to me they won't do anything to evict my branch offices, which would give me casus belli against them.
What does my megacorporation do, you might ask? Fast food.
I tricked other empires' peoples into emigrating to my empire, and I genetically altered them to be space cows. I slaughter them by the billions and feed them to their own people in the form of cheap, unhealthy, convenience food, and the other empires are too afraid of me to do anything but quietly engage in empire-wide cannibalism in humiliating obeisance. I am making a shitload of money off this I don't even need, because half the worlds in my empire are ecumenopoli and I have a Dyson sphere.
The question posed in the thread title probably isn't one I should answer.
My next playthrough is going to be with post-apocalyptic fanatic purifiers!