The S&P 500 cratered 4.2% to 1,087.69 last week, ushering in a long-awaited official correction as concerns of the European debt crisis, the flash crash, and financial regulatory reform rattled investor confidence.

Pops and drops
Here are the five biggest S&P 500 upticks and five biggest S&P 500 drops of last week (measured Friday close to Friday close):

Winners on the week:

Company

Percentage Gain on the Week

Pactiv (NYSE: PTV)

20.9%

Dean Foods

8.5%

Apollo Group (Nasdaq: APOL)

5.2%

Tellabs (Nasdaq: TLAB)

4.9%

DeVry (NYSE: DV)

4.9%

Source: Capital IQ (a division of Standard & Poor's).

Losers on the week:

Company

Percentage Loss on the Week

Sears Holdings (Nasdaq: SHLD)

(18.2%)

Massey Energy (NYSE: MEE)

(15.8%)

Goodyear Tire & Rubber

(13.2%)

Zions Bancorporation

(12.9%)

Dell (Nasdaq: DELL)

(11.9%)

Source: Capital IQ (a division of Standard & Poor's).

A closer look
Shares of Sears Holdings took a beating last week after reporting a fiscal first quarter that matched up negatively to other big-box retailers. The owner and operator of retail chains Sears and Kmart reported earnings that tumbled 39% on practically flat sales and increased promotions for appliances and home electronics. Sears' results contrast with other retailers that are beginning to show improved results (increases in revenue, gross margins, and decreased usage of discounts) based on the emerging economic recovery. Still, Sears Holdings has seen improvement thanks to state programs that promote energy-efficient appliances, progress with its online operations, and its Kmart stores, which saw their third straight quarter of gains in comparable-store gains.

Shares of Dell slipped last week after reporting first-quarter gross margins that disappointed. Margins were hit by rising component costs. Despite disappointing margins, the computer maker confirmed early stages of a rebound in corporate demand for technology. Commercial demand continued to grow and Dell is optimistic for the trend to continue through the balance of the year. However, the company did warn of seasonal weakness in orders from large business customers in the second quarter and beginning of the third quarter.

One bright spot last week was Pactiv, which shot up after reports that paper and packing company Georgia-Pacific and New Zealand-based Rank Group expressed interest in buying the maker of Hefty trash bags. This adds to reports from The Wall Street Journal that private equity firm Apollo Global Management was already in buyout talks with Pactiv.

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Fool contributor Jennifer Schonberger does not own shares of any of the companies mentioned in this article. You can follow her on Twitter. Apollo Group is a Motley Fool Inside Value recommendation. The Fool has a disclosure policy.