Warren Buffett, a long-time critic of cryptocurrency who once said it’s “rat poison squared,” has profited substantially from his investment in Nubank, a financial institution with multiple crypto-related services. Nubank is a leading fintech platform in South America, serving more than 85 customers throughout Brazil, Colombia and Mexico, as well as crypto-related services to more than 1.35 million customers. These services include a digital financial platform for trading Bitcoin and Ethereum, a trading platform with a Bitcoin ETF product and a Nubank loyalty token running on the Polygon block…