Warren Buffett, the famed billionaire investor, has been one of the loudest bitcoin and crypto critics amid a U.S. "war" on bitcoin.

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The bitcoin price has swung wildly over the last few years, soaring through the first half of 2023 as traders gear up for what could be a $17.7 trillion earthquake hitting the market.

Now, as a crisis is threatening to engulf the U.S. dollar, a new analysis of Warren Buffett's Berkshire Hathaway BRK.B stock portfolio has revealed the Oracle of Omaha's best-performing investment this year is bitcoin and crypto-friendly Nubank.

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Buffett's Berkshire Hathaway invested $500 million in Brazil's Nubank in June 2021 ahead of its initial public offering (IPO) later that year. Buffett's Nubank holding is thought to be now worth around $840 million after he plowed another $250 million into the startup bank during its IPO.

The bank, which allows users to trade bitcoin and other cryptocurrencies and earlier this year launched its own cryptocurrency called nucoin, has seen its stock price rocket over 100% so far this year amid soaring revenue and customer numbers.

Analysis by Business Insider showed Nubank's stock market performance has topped Buffett's other holdings, including giants Amazon AMZN , Apple AAPL , Coca-Cola, Bank of America BAC , and Kraft Heinz.

Earlier this year, Buffett dismissed bitcoin as a "gambling token" in an interview with CNBC, saying bitcoin "doesn't have any intrinsic value ... but that doesn't stop people from wanting to play the roulette wheel."

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Buffett has regularly slammed bitcoin and those that trade crypto, claiming during Berkshire Hathaway's 2022 annual shareholder meeting that bitcoin and crypto are not productive assets and branding bitcoin "rat poison squared."

"If you told me you owned all the bitcoin in the world and you offered it to me for $25, I wouldn't take it," Buffett said. "Whether it goes up or down in the next year, or five or 10 years, I don’t know. But the one thing I’m pretty sure of is that it doesn’t produce anything."

Charlie Munger, Buffett's right-hand man at Berkshire Hathaway, has also heavily criticized bitcoin, just last week calling it "the stupidest investment I ever saw," during Zoom’s Zoomtopia conference, Fortune reported.