Maybe Hangzhou? Situated in China's 4th richest province, and within the wealthy Jiangnan region, it has great potential due to its geographical position. However, as of now, it is eclipsed economically by Shanghai, a much younger city (people of the region even call Shanghai Benbang--roughly translating to "centerpiece city"). This is a far cry from Hangzhou's status of China's largest city during the Southern Song Dynasty, and that is very impressive when you note that the Song comprised of 80% of the world's GDP in its heyday. Later on, Hangzhou was eclipsed politically by Nanjing in the early Ming Dynasty, during which Nanjing served for a time as China's capital, and was of course overtaken by Shanghai during the Qing Dynasty.
As of now however, Hangzhou still has one asset--tourism. It is also one of China's most modern, automated cities and has absolutely beautiful scenery. If China was to be more Southern-oriented than OTL, and also historically focused more on the economy, Hangzhou could very likely have remained China's number 1 city to this very day.