That said, of the eight stablecoins S&P reviewed, several received lackluster scores. Most notably Tether’s USDT, the largest stablecoin by market cap and most used crypto asset in terms of trading volume, was given the fourth-lowest score in range from 1 to 5. Meanwhile MakerDAO’s dai (DAI), popular across decentralized finance (DeFi), and the Justin Sun-backed TrueUSD, the fourth and fifth largest stablecoins, respectively, were also given low scores.