While the S&P 500 (^GSPC) includes industry leaders, not every stock in the index is a winner. Some companies are past their prime, weighed down by poor execution, weak financials, or structural headwinds.

Picking the right S&P 500 stocks requires more than just buying big names, and that’s where StockStory comes in. Keeping that in mind, here is one S&P 500 stock that could deliver good returns and two that could be in trouble.

Two Stocks to Sell:

Walmart (WMT)

Market Cap: $761.3 billion

Known for its large-format Supercenters, Walmart (NYSE:WMT) is a retail pioneer that serves a budget-conscious consumer who is looking for a wide range of products under one roof.

Why Does WMT Fall Short?

1. Sizable revenue base leads to growth challenges as its 5.4% annual revenue increases over the last five years fell short of other consumer retail companies

2. Widely-available products (and therefore stiff competition) result in an inferior gross margin of 24.6% that must be offset through higher volumes

3. Subpar operating margin of 4.2% constrains its ability to invest in process improvements or effectively respond to new competitive threats

At $94.70 per share, Walmart trades at 34.5x forward price-to-earnings. Check out our free in-depth research report to learn more about why WMT doesn’t pass our bar .

Emerson Electric (EMR)

Market Cap: $56.99 billion

Founded in 1890, Emerson Electric (NYSE:EMR) is a multinational technology and engineering company providing solutions in the industrial, commercial, and residential markets.

Why Does EMR Worry Us?

1. Products and services are facing end-market challenges during this cycle, as seen in its flat sales over the last five years

2. Estimated sales growth of 4.7% for the next 12 months implies demand will slow from its two-year trend

3. Waning returns on capital imply its previous profit engines are losing steam

Emerson Electric is trading at $101.08 per share, or 16.7x forward price-to-earnings. To fully understand why you should be careful with EMR, check out our full research report (it’s free) .

One Stock to Buy:

Quanta (PWR)

Market Cap: $40.67 billion

A construction engineering services company, Quanta (NYSE:PWR) provides infrastructure solutions to a variety of sectors, including energy and communications.

Why Should You Buy PWR?

1. Sales pipeline is in good shape as its backlog averaged 23.8% growth over the past two years

2. Projected revenue growth of 13.5% for the next 12 months suggests its momentum from the last two years will persist

3. Earnings per share grew by 18.6% annually over the last two years and trumped its peers