Analyst Mike Mayo has long been one of the loudest and most prominent critics of big banks, including Citigroup (NYSE:C). But Wednesday he had some competition from the nonprofessionals.

Mayo showed up at Citigroup's annual meeting with some tough questions for Chairman Michael O'Neill and Chief Executive Michael Corbat. But his arrival might have actually been a relief for the executives, who warmed up by fielding questions, complaints and testimonials from a group of impassioned shareholders.

As in previous years, the investors who dominated the meeting were most upset about the bank's share price, its penny dividend, their lack of access to the board of directors and even a reverse stock split in 2011 that shrank the number of shares each investor held (though it helped boost each share's value).

"The price is still where it is, it stinks, and you guys haven't done anything for shareholders since you've been here," Russell Forenza, a shareholder and fixture at Citigroup's annual meetings, said during the first of his several trips to the microphone. (Three hours later, Corbat and O'Neill had apparently managed to win over Forenza, who told them in his last appearance that he would give them "an A" for their performance.)

Mayo, of brokerage CLSA, was apparently impressed by his fellow audience members. "People call me aggressive. But after seeing the questions here today…," he remarked, to laughter, during his first trip to the microphone.

The competition may have helped Mayo step up his game: later in the meeting, he returned to the microphone with what he called "a four-part question." O'Neill and Corbat answered patiently, as they had most of the questions Wednesday. All things considered, it's amazing the meeting only took three hours.

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