Right now, the Universa Investments founder, whose fund aims to protect clients during black swan events, says the financial system is most vulnerable to "the greatest credit bubble of human history."

"If this credit bubble ever pops, it's going to be the most catastrophic market failure that anyone has ever read about -- but let's hope that doesn't happen," Spitznagel, Miami-based Universa's chief investment officer, said Thursday in a telephone interview. "We've gotten ourselves into a tough spot."

Spitznagel, 51, insists he's not a "doom and gloomer." He's long been critical of central banks keeping interest rates near-zero or even negative, which he says has propped up asset values and encouraged excessive borrowing. Officials around the world are now tightening monetary policy to combat elevated inflation.