Mandate of Heaven

Needs All Under Heaven. You need to own the Hegemony of China title - seized through the expansion's Dynastic Cycle, whose instability windows are your opening - and then name your new Imperial Dynasty when prompted; the achievement wants both the title and the naming. The wiki is light on a step-by-step here, but it explicitly pairs this with Fishing in China (same Hegemony requirement, from a Norse count, no less), so if you're going for the mad one anyway, this falls out of it.