The health insurance giant can't seem to catch a break nowadays. UnitedHealth Group (UNH 1.57%) has been a staple in the healthcare world for decades and is one of the largest companies in the world, with a market cap of around $280 billion as of Aug. 18. Unfortunately, the company was much more valuable before a recent string of events sent the stock plummeting. Had you invested$1,000 into UnitedHealth Group stock three years ago (using Aug. 18, 2022, as the starting point), your investment would only be ...