Best CB in eu4?

Just did a Qing run and man, I gotta say that the Unify China CB gets my pick as the best in the game. 50% war score cost for annexing Provences in China… oh and you basically get free cores on all of China too. Of course the issue with crowing this the best CB is that it only works in the subcontinent, but it’s so good and there’s a LOT of dev in China. Anyway, what do y’all think is the best CB?