Citigroup was the only mega-bank, aside from Bank of America, to receive more than one round of taxpayer bailout money. It received a total of $45 billion from the government.

The government converted $25 billion into an ownership stake in the bank, the last of which the government sold in December 2010. Citigroup repaid the remaining $20 billion in December 2009.

The bank also benefited from billions more in government subsidies and guarantees against losses on bad investments.

As the crisis erupted in September 2008, Pandit suffered a bruising embarrassment. His bank announced it would buy the bulk of Wachovia, which was being crushed by lousy, complex mortgage investments. Citi would get a fire-sale price and emerge from the crisis a rescuer, rather than a victim.

But four days later, Wells Fargo charged in with another offer. It elbowed Citi out of the way and won the approval of shareholders and regulators.

Citi survived those critical months, but its reputation was tattered. In March 2009, as the crisis raged, President Barack Obama ordered the Treasury Department to consider breaking up Citigroup and removing its executives, according to a behind-the-scenes book about the crisis published last year by journalist Ron Suskind.

Treasury Secretary Timothy Geithner ignored Obama’s request, according to Suskind’s account. Geithner and the White House have disputed his version of events.

Pandit had another powerful opponent in Sheila Bair, an influential bank regulator who ran the Federal Deposit Insurance Corp. during the crisis. Bair wanted the government to fire Pandit after the taxpayer bailouts and government guarantees. Geithner disagreed, and Pandit kept his job.

In an interview with CNBC after Pandit’s departure was announced, Bair said Citigroup has lacked ‘‘a clear strategic direction and focus’’ under Pandit, and said shareholders have been unhappy.

She said that the bank would benefit from a CEO like Corbat with commercial banking experience, as opposed to Pandit’s background in investment banking, and that the move would be beneficial for shareholders.

In a book published last month, Bair said Pandit had been installed as CEO by Robert Rubin, a former treasury secretary who was the bank’s chairman at the time, ‘‘to clean up the mess at Citi.’’

‘‘I thought he had been a poor choice,’’ Bair wrote.

Pandit nursed the bank back to annual profitability in 2010. But Citigroup’s troubles continued, even after the Treasury Department sold the last of its stake.

Its stock price plunged 44 percent in 2011. Bank stocks suffered broad declines last year because of the European debt crisis, fear of a second recession and uncertainty over the federal borrowing limit. So far in 2012, Citigroup stock has recovered about half its loss from last year.

In March, Citigroup surprised observers by failing an annual financial checkup administered by the Federal Reserve, its main regulator. The Fed refused to let Citi raise its dividend because it said the bank, unlike its peers, did not have enough capital to pay shareholders and still withstand a financial crisis worse than 2008.

Investors voiced their frustration by voting this spring to reject Pandit’s pay package for 2011, which was valued at $15 million — roughly in line with most of his counterparts — and included an additional $10 million in retention pay due to him in 2013 if he stayed on as CEO. Pandit received none of the retention money, a bank spokeswoman said.

The investor vote was the first time shareholders had dinged a Wall Street bank under a provision of the 2010 financial overhaul law that gives them a non-binding vote on executive pay.

Pandit had accepted a token $1 in compensation in 2010. In 2008, Pandit’s compensation package was valued at $38.2 million.

Last month, Citigroup received much less money than it had hoped for when it sold its share of the retail brokerage Morgan Stanley Smith Barney. The bad estimate forced Citigroup to take a heavy write-down.

Along with Bank of America, it is the only mega-bank still paying its shareholders only a token penny dividend each quarter.