Very rarely can a single stock make you a millionaire. Icahn Enterprises (IEP 1.52%) is no exception. Investing in this stock should be part of a diversified approach focused on long-term results. But that doesn't mean shares can't provide meaningful upside to your investment portfolio, especially at today's depressed prices.In the past year, Icahn Enterprises stock has lost roughly two-thirds of its value. Many investors are taking a closer look, given the company is controlled by a well-respected investor ...