Heading into trading on Monday, the S&P 500 was down around 5% to start 2025. The three worst-performing stocks on the broad index as of Monday were Deckers Outdoor (NYSE: DECK), Tesla (NASDAQ: TSLA), and On Semiconductor (NASDAQ: ON). The S&P 500 stock down the most after the first quarter of 2025 is Deckers Outdoor, a footwear company that is struggling mightily despite posting what seemed to be decent results in its most recent quarter.