When Mark L. Hart III, a hedge fund investor based in Texas, makes an investment bet, he does it in the style of his home state: big time.

Since 2007, his winners have included high-risk, high-return wagers that the United States housing market would collapse and that Greece would go bankrupt.

But Mr. Hart’s most audacious gamble to date may well be the one he is making on China. He is betting that the mini-devaluation of China’s currency last month was a mere appetizer to a 50 percent currency implosion that he predicts will come when foreign investors pull their money out of China.

Such an extreme drop in China’s currency, the renminbi, would propel a broader rout in emerging-market currencies — from South Korea to Turkey to Brazil — and result in a sustained global slump as China’s borrowing binge grinds to a halt.