Although the boom in banking anticipated by some buyout firms during the financial crisis largely failed to materialize, a few did harvest impressive profits. Investors in Coral Gables, Fla.-based BankUnited scored big when the bank priced its $783 million initial public offering at the end of January, allowing CEO John Kanas, W.L. Ross & Co. LLC, Blackstone Group LP and Carlyle Group to rack up a more than 130% partly realized gain in less than two years.

Not bad. Still, the biggest winner of the crisis so far looks like Warburg Pincus. The firm, which has a long history in financial services, largely eschewed trying to buy financial companies and pursued a recapitalization strategy that has paid huge dividends. The firm's success, despite one notable misstep in bond insurer MBIA Inc., suggests that Warburg chose the right strategy when it decided to inject liquidity into banks rather than struggle against regulatory obstacles by trying to buy failed or failing institutions.

"The agencies put the kibosh on private equity," says one attorney focused on banking, noting that many PE firms had been jostling to buy failed banks, then used the initial investment to roll up other banks.

With few approved deals, that strategy largely flopped. But Warburg's financial services group, co-headed by former J.P. Morgan Chase & Co. investment banking head David Coulter and former UBS banker Michael Martin, and including partner Daniel Zilberman, has hit several home runs over the past two years by taking more traditional investment routes.

Take Warburg's $162 million investment in Webster Financial Corp., made in three tranches, the first of which was in July 2009. Its investment in the Waterbury, Conn.-based bank came at around $6 a share, after accounting for the value of warrants received as part of the equity infusion. As of Feb. 1, Webster shares were trading at $23.23, a gain of 3.85 times.

That deal is the firm's biggest winner, but other investments made during and after the crisis are also paying off. A $230 million investment for a 20% stake in Primerica Inc., the term life insurance business spun off by Citigroup Inc. last year, was made at $12.50 a share, again including the warrants. The stock closed at $24.69 on Feb. 1.

The firm made a $171 million investment in Sterling Financial Corp., a bank based in Spokane, Wash., at $12.60 a share, including warrants. The shares traded at $18 on Feb. 1. And it placed $150 million, or $6.05 a share, into Boyertown, Pa.'s National Penn Bancshares Inc. in October 2010. National Penn was recently trading at $8.36.

This success continues a tradition of sorts at Warburg Pincus. The firm scored in the S&L crisis of the late '80s when it bought a 20% stake in Pittsburgh's Mellon Bank Corp. in 1988, which yielded a 30% compounded annual return when it sold its stake over eight years. Over a decade later, Warburg had an even bigger success, taking a 12.5% stake in Dime Bancorp Inc. in 2000 and turning the $238 million investment into $750 million in less than two years when Washington Mutual Inc. bought Dime for $5 billion.

"They've done very well," admits one financial services banker, citing the Webster deal as a model for investing in the sector. Carlyle has also worked to inject money into banks after struggling to buy failed institutions from the Federal Deposit Insurance Corp., the effort led by the firm's Olivier Sarkozy and Randal Quarles. On Nov. 1, Carlyle partnered with Stephens Group LLC, an investment banking boutique in Little Rock, Ark., and privately held Nonami LLC to inject $125 million in Brand Group Holdings Inc., a privately held bank based in Lawrenceville, Ga.

Carlyle also worked with Anchorage Capital Group LLC of New York to invest $98.6 million in Honolulu-based Central Pacific Financial Corp., as part of a larger $325 million capital raising. The investors agreed to buy the bank's common stock for 50 cents per share, a 50% discount to its prior-day close, for a 24.9% stake each. Although the bank is still struggling, the investment has more than tripled with the stock trading at $1.53 on Feb. 1.

Of course, Warburg's triumphs are marred a bit by MBIA. The firm invested $815 million in the bond insurer at $15 a share (in three separate equity infusions plus warrants), then saw MBIA's stock plunge to a low of $2.53 per share in March 2009. Since then, the stock has rebounded, hitting a 52-week high of $14.90 in January, before retreating to $10.92 on Feb. 1.