Citron Research founder Andrew Left worked investors up after shorting GameStop in 2021. The short seller could see a similar reaction targeting the cryptocurrency sector.

What Happened: Left bet against GameStop in 2021. He believed the video game retailer's valuation was too high, citing declining sales.

On Thursday, Left told Benzinga he went short on GameStop again over the past week.

Left remains divided on cryptocurrency. He was previously against Bitcoin (CRYPTO: BTC), Ethereum (CRYPTO: ETH) and non-fungible tokens (NFTs). Since then, he has somewhat reversed his position and is now long Bitcoin.

"I get Bitcoin," Left said. "I'm long Bitcoin and I'm short Ether."

If Bitcoin goes down 20%, Ether could go down 30%, he added.

The Citron Research founder also predicts Ether will be labeled a security. It won't get regulators' stamp of approval like Bitcoin, he says.

The U.S. Securities and Exchange Commission (SEC) approved Bitcoin ETFs on Jan. 10.

Left said he remains cautious on Bitcoin. You could wake up tomorrow and Bitcoin could be $42,000, or it could be $80,000, he says.

Left Bearish On Coinbase: Left also thinks one of the largest cryptocurrency exchanges in the world is overvalued.

"I still look at Coinbase as an exchange," Left said of Coinbase Global (NASDAQ:COIN).

Left asked if everyone holds on to Bitcoin and doesn't sell and s—coins, aka altcoins go away, where's Coinbase's business?

"Let's get rid of s—coins, I don't believe in them."

BTC, ETH, COIN Price Action: Bitcoin trades at $65,112.32 at the time of writing and is up 47.3% year-to-date in 2024.

Ethereum trades at $2,950.48 at the time of writing and is up 25.4% year-to-date in 2024.

Coinbase shares trade at $201.11 and are up 15.6% year-to-date in 2024.