At both the Democratic and Republican conventions, the nation’s biggest banks were again cast as the bad guys, criticized as being too big and too risky.

This week, as the Olympic Games begin in Brazil, one of the big banks, Citigroup, is offering a rebuttal with a series of prime-time television and digital ads featuring images of sweaty athletes, the Space Shuttle and an early A.T.M.

“Our business is helping Americans make progress,” the ad’s narrator says, as a runner with a prosthetic leg sprints down a track.

Since the 2008 financial crisis, American banks have spent millions of dollars on advertising, consultants and social media initiatives, seeking to portray themselves as something other than greedy risk-takers. And yet, eight years later, anger and resentment persists.