I'll bet that there are hundreds of these in China. Just go to Google Maps (or Baidu Maps), zoom in to some mountain or rural area, and look for any route with a number that's twisty. China's numbered roads are not legislated, let alone signed, inside urban areas, so maintenance gaps are rife. It's also extremely difficult to legally drive in China; you need a Chinese license, and a decent vehicle (hopefully 4wd). And the drivers in China are hell. Thankfully, Google Maps is the only Google service not blocked in China... but only for the Chinese edition. So good luck getting anywhere if you don't know Chinese. Even so, it is very inaccurate for mapping China: routes haphazardly routed through urban cores where no signage exists, routes splitting in half, highways under construction that just terminate in the middle of nowhere with no interchange, you name it.
My favorites:
* Fujian S201: several disjoined segments along the coast, like FL-A1A on steroids
* Inner Mongolia S213: It starts out near Bayan Nur, which is already a great deal away from everyone else, at a junction with a national highway, at two places according to Google Maps. Good luck figuring out which one is real. You're then going to have to pray that you don't screw up at the next such split, because that one dead ends. And if you do take the right way this time, you'll have to follow the route through poorly signed turns and mountain ranges... only for it to end in god-knows-where several dozen kilos later.
* G219: remote, runs through no major cities, unpaved in many places, runs through Xinjiang, Tibet, and the disputed region of Aksai Chin (see below for evidence as to why this is so difficult), 2,086 km long, and up to 5,050 km high. Why on earth would anyone even dare to try clinch this one?
* G318: the longest national road in China at 5,476 km, from Shanghai to the Nepal border. A lot of high altitude sections, many twists and turns, and good luck even getting permission to enter Tibet, a region officially closed to road travel to foreigners due to political unrest. Even if you manage to do all of the above, it might all be for nothing, as the final stretch to the border is intermittently open due to hazardous rockfall (landslides have also turned the border towns to ghost towns). I'm not even sure if there's any place to make a U-turn there! As such, I believe that G318 wins the golden crown for "hardest road in the world to clinch".