Exlor
Okay, lemming and denial memes aside, if he has to kill one plan, it's gotta be the Polymath's. It's straight up the most threatening for him. She's inevitably his enemy due to the Metal Scroll, the other human factions will despise him if he enables her to be the sole ruler, and he'd be crazy to isolate himself and give supreme power to someone who he will almost certainly have to confront at some point...