LONDON—International investors that have been piling into China in recent years are now bracing for one of its great falls as the troubles of over-indebted property giant China Evergrande come to a head. The developer’s woes have been snowballing since May. Dwindling resources, set against $305 billion of liabilities, have wiped nearly 80 percent off its stock and bond prices. An $80 million bond coupon payment now looms next week. What happens then is unclear. Bankers have said Evergrande will most likely miss the payment and go into a kind of suspended animation where authorities step in and sell some of its assets; but it could easily get messy. “We will have to see what happens,” said Sid Dahiya, head of EM corporate bonds at abrdn, formerly Aberdeen Standard, in London, which holds a small sliver of the bonds. “They are probably working on a deal in the background, but …