Vermont Senator Bernie Sanders assailed Hillary Clinton as financially beholden to Wall Street and unable to be tough on the industry as they faced off Sunday in the most adversarial Democratic presidential debate yet.

Sanders, who's built his campaign on populist anger directed at the big banks, charged that he and the former secretary of state have many differences on Wall Street and “the first difference is I don’t take money from big banks, I don’t get personal speaking fees from Goldman Sachs."

Clinton was paid by $675,000 for three speeches she gave to the firm in 2013 and her husband, former President Bill Clinton, has also been paid for appearances at Goldman events. She's also raised millions of dollars in campaign contributions from employees of banks, hedge funds and other financial services companies.

She ignored Sanders' comments on the speaking fees and touted herself as building on the accomplishments of the Obama administration, while Sanders argued for a broader shift from the status quo.

Sanders is calling for a broader overhaul of laws and wants to enact an updated version of the Glass-Steagall Act, repealed while Bill Clinton was in the White House, while Clinton supports more incremental change building on the Dodd-Frank Act, signed into law by President Barack Obama.

Clinton argued that the gap between her and Sanders is not particularly large. “There’s not daylight on the basic premise that there should be no bank too big to fail and no individual too powerful to jail," she said at the NBC-YouTube Democratic Candidates Debate in Charleston, S.C., the final face-off before the Iowa caucuses on Feb. 1.

Then, referencing an ad released by the Sanders campaign this week that her team described as an attack on her and President Barack Obama, she said that “where we disagree is the comments that Senator Sanders has made that don’t just affect me, I can take that, but he’s criticized President Obama for taking donations from Wall Street and President Obama has led our country out of the great recession."

In the state where she and the president had an acrimonious battle during their 2008 battle for the Democratic nomination, Clinton defended her former rival and boss. "Senator Sanders called him weak, disappointing. He even in 2011 publicly sought someone to run in a primary against President Obama."

The third candidate in the debate, former Maryland Governor Martin O'Malley interjected that he would be stronger. "The truth of the matter, Secretary Clinton, you do not go as far in reining in Wall Street as I would," he said. Clinton responded by noting that O'Malley fundraised on Wall Street while leading the Democratic Governors Association.

Clinton and Sanders clashed over gun control and the future of health insurance in the final Democratic presidential debate before the Iowa caucuses, with Clinton warning that Sanders’ hours-old plan to move to universal Medicare coverage risks further dividing the nation and jeopardizing the gains under the Affordable Care Act.

"What a Medicare-for-all program does is finally provide in this country health care for every man woman and child as a right," Sanders said, noting that even after the expanded coverage created by Obama's Affordable Care Act, "29 million people still have no health insurance."

Clinton countered that Sanders' plan is impractical. Noting that it took the Democratic Party six decades to enact the Affordable Care Act, which she called "one of the greatest accomplishments" of the Obama administrations, she said: "To tear it up and start over again pushing our country back  into that kind of contentious debate I think is the wrong direction."