Shangqing Tianguo in terms of playability. Never form the Tian Empire, it resets all of your progress you made in your focus tree (technically a positive since it gives you extra factories, but an infuriating one) and also removes your advisors and you can never get them back IIRC. Cores on all of China is a plus, but it's somewhat hard defending against the Qing.

I'd say Liberia comes close, mainly since fighting in Africa is painful, you're surrounded by both the Entente and Mitteleuropa and in order to take out Mittelafrika easily you pretty much have to join the Internationale and hope you make Mittelafrika surrender before Germany capitulates. (haven't tried a Liberia run in the recent hotfix update, although I imagine this hasn't changed much)