David Tepper is the founder and president of Appaloosa Management, one of the 15 most successful hedge funds in history as measured by net gains since inception, according to LCH Investments. During the fourth quarter, Tepper sold 600,000 shares of Amazon (NASDAQ: AMZN), trimming his position by 19%. Vistra is a power-generation company that could benefit if artificial intelligence boosts data center electricity demand.