At the height of the housing bubble, hedge-fund manager Paul Singer was shorting subprime mortgages. By the spring of 2007, he was warning regulators on both sides of the Atlantic that the world was facing a major financial crisis.

They ignored him. Now the founder of Elliott Management says the biggest banks are headed for another credit meltdown. Among the likely triggers for the next crisis, Mr. Singer sees one leading candidate: Monetary policy "is extremely risky," he says, "the risk being massive inflation."

In...