When you decide diplo-annexation takes too
long, and you release your vassal just so you can attack 'em again later.
When you invade someone just because you'd like to use one of their systems as a convenient wormhole station hub.
When you intentionally scare your neighbors into forming a federation and get into a war with that federation, just so you can farm debris of ALL their best ship components at once.
When you trap an outmatched enemy fleet that uses hyperdrives, and let them EFTL out only to immediately catch and reengage them, keeping them bouncing over and over until they finally feel the sweet release of death - all in order to get multiple debris piles out of one fleet.
I had no one who liked arid worlds, so I sent one of my base pops to colonize it anyway. If I genetically modified the initial pop, though, the planet would still end up with a bunch of those pops with low habitability - so i intentionally moved the first pop off a food tile, waited for the growing pop to die from starvation, THEN modded the initial pop and put them back on food. All so I don't have to use resettlement - that would be evil!
Conquer an enemy capital, rename it
[Khusrau's] Better [Antioch]