One of Wall Street's biggest crypto skeptics is taking fresh aim at bitcoin amid its steep sell-off.Nouriel Roubini — also known as "Dr. Doom" for his frequently apocalyptic predictions on markets and the economy — doubled down on his view that bitcoin is far from being an inflation hedge and is a "pseudo-asset class." Bitcoin, which entered bear market territory late last year, traded around $67,400 on Wednesday, down 45% from its peak in late October."Calling Bitcoin or any other crypto vehicle a 'currency' has always been bogus. It is neither a unit of account, a scalable means of payment, nor a stable store of value," Roubini wrote in an op-ed for Project Syndicate earlier this month.Roubini, who has blasted bitcoin in the past as a "Ponzi Game" associated with criminal activity and said he believed the token was in "the mother of all bubbles," pointed to the crypto's potential use in illegal transactions. He also said that crypto broadly poses a risk to the financial system as lawmakers integrate it further into traditional banking.In particular, he highlighted the GENIUS Act, and said the landmark stablecoin bill should be remembered as the "Reckless Idiot Act," partly because the bill specifies that stablecoins do not have lender-of-last resort or deposit insurance benefits.The push among some players in the crypto industry to allow interest payments on stablecoins could further "undermine the foundations of the banking system," he added."Thus, all it would take to incite a panic and trigger a bank run is for a few bad apples in pseudo-libertarian US states to mis-invest their holdings or place their deposits in weak institutions," Roubini speculated. "This is a political and financial stability issue, and few are as serious or as sensitive," he later added.Bitcoin's pronounced sell-off has slashed the token's value nearly in half. Should its decline lead to a true bitcoin winter, some forecasters see the coin dropping to as low as $31,000, a more than 50% drop from the token's current levels.