No matter the market, there will always be losers, a few lagging disappointments holding back a Wall Street rally or several big losers leading a bearish day. The S&P 500 (SNPINDEX:^GSPC) barely budged today, falling flat after rising earlier in the day. However, several big-name stocks took big losses and made investors pull their hair out in frustration. Here are the three worst stocks today that you need to know about – from credit cards to retail, these stocks put a dent in Wall Street's Wednesday.

Exelon's earnings drag down shares
Power company Exelon (NYSE:EXC) ranked among the S&P's worst today with shares down around 2.8% for the day. Exelon was a victim of earnings season's wrath despite a relatively strong report. The company's net income jumped by 71% and revenue also rose year over year. However, both Exelon's adjusted EPS mark and its revenue missed on analyst projections. This stock hasn't done very well year to date compared to the overall market's gains, but Exelon confirmed its full-year outlook today and looks on pace for a modest second half as electricity prices and demand have fallen in recent years.

Credit card titan Visa (NYSE:V) took a big hit as shares fell a whopping 7.5%. Blame the courts for this one: A Washington, D.C., district court judge ruled  that the Federal Reserve's limit on debit card "swipe" fees implemented in the wake of the 2010 Dodd-Frank law is too high. Retailers have argued against the 21-cent cap the law implemented, claiming that Congress intended for a lower limit to the fees.

Visa and fellow card giant MasterCard collect the swipe fees and pass them on to card issuers. Since both companies operate heavily in the debit card space, the ruling took down shares of both companies, although MasterCard rebounded to gains on the day. Visa, which operates a larger payment network than its rival, wasn't so fortunate. Still, with consumer confidence on the rise in the U.S. and the economy slowly rising, Visa's hardly in a tight spot because of one ruling. If anything, today's big fall is a great opportunity to buy into an otherwise solid stock on a dip.

That ruling couldn't help one retailer, however. J.C. Penney (NYSE:JCP) investors have gotten used to a depressing year from this stock, but today's gut-wrenching plunge drove down shares by an eye-popping 10.2% as this stock bottomed out among the S&P 500's losers.

Shares collapsed into freefall near the end of the day after it was reported that clothing industry lender CIT will no longer support smaller firms that manufacture products for J.C. Penney. CIT reportedly made the decision after getting a look at J.C. Penney's financials, which haven't impressed anyone this year. The retailer has struggled to dig out of the hole exacerbated by former CEO Ron Johnson, whose failed turnaround attempt has mired the firm in a toxic mess of falling same-store sales and a plunging stock price. Until this retailer shows signs of life, J.C. Penney is one diving stock that isn't worth a turnaround bet.

Fool contributor Dan Carroll has no position in any stocks mentioned. The Motley Fool recommends Exelon and Visa. It recommends and owns shares of MasterCard. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.