Non-Qin Unified China

It's a well-known theme of AH to have disunited or differently united Germanies and Italies in the 19th century. However, I would like to ask a similar question for ancient China. In the 3rd century BC, the state of Qin one by one gulped up the other Chinese states one by one until in 221 BC, all of China was unified under Qin Shi Huang.

So, what I am going to ask is, which of the other states has the best chances of unifying China? And also, what would be a reasonable POD for making this happen, and finally, what would be the consequences?
 
Early on, the Huanghe states seemed pretty scared of Chu, but I don't think at that point their opposition could easily be reduced enough for a complete steamroller.

I don't feel that at any other point in history any state except Qin had the necessary will and the necessary capability for a total conquest, so the divergence would probably have to be some time before the actual takeover.
 
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