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George Washington -

The first president of the United States owned slaves throughout his lifetime, but as he grew older he came to regret it. "The unfortunate condition of the persons, whose labor in part I employed, has been the only unavoidable subject of regret,” he wrote.

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George Washington -

“I never mean (unless some particular circumstance should compel me to it) to possess another slave by purchase: it being among my first wishes to see some plan adopted by the legislature by which slavery in the Country may be abolished by slow, sure, & imperceptible degrees,” wrote Washington. When the president died, a provision in his will ensured the enslaved people he owned were freed.

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John Quincy Adams -

The sixth US president served from 1825 to 1829. As soon as he took office, he signed the Indian Springs Treaty. The treaty essentially forced the Creek Nation to give up their land (now Georgia) and move west.

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John Quincy Adams -

After meeting with leaders of the Creek Nation, Adam regretted signing the treaty and tried to annul it, but to no avail. The Creek Nation ended up giving up all their land in the end.

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John Quincy Adams -

“We have talked of benevolence and humanity, and preached them into civilization," Adams wrote in his personal diary. "But none of this benevolence is felt where the right of the Indian comes in collision with the interest of the white man,” he added.

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Andrew Jackson -

The seventh president of the United States regretted not resolving conflicts with his rivals. Shortly after Martin Van Buren was elected, Jackson was asked about his regrets over the last eight years. His reply: “That I didn’t shoot Henry Clay and I didn’t hang John C. Calhoun.”

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Dwight D. Eisenhower -

President Eisenhower (R) regretted appointing Earl Warren (L) as Chief Justice of the Supreme Court. Warren went on to lead the Court in a series of liberal (and historical) decisions that Eisenhower wasn’t too pleased about.

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Dwight D. Eisenhower -

The president later said that appointing Earl Warren as Chief Justice of the Supreme Court was "the biggest damned-fool mistake I ever made."

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Richard Nixon -

Delaying the North Vietnam bombings from 1969 to 1972 was President Nixon’s biggest regret while in office. Nixon believed that if he had made the move in 1969, the war would have ended earlier.

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Richard Nixon -

''I wanted to do it,'' he said. ''I talked to Henry Kissinger about it, but we were stuck with the bombing halt that we had inherited from the Johnson administration, with Paris peace talks. I knew that, just like the cease-fire talks down here in Nicaragua, I didn't trust them at all. And they proved to be, of course, phony,” added Nixon.

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Richard Nixon -

The Watergate scandal, on the other hand, didn’t seem to rank high on the late president’s list of regrets. Though Richard Nixon did confess in an interview with David Frost in 1977 that he apologized to those in the White House the day he announced his resignation.

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Jimmy Carter -

President Carter admitted that he deeply regretted how he handled the Iran hostage crisis. In 1979, 52 American diplomats and citizens were held hostage in the country for 444 days.

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Jimmy Carter -

“I wish I had one more helicopter to get the hostages, and we had rescued them, and I was reelected,” Carter said in an interview in 2015.

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Ronald Reagan -

Ronald Reagan regretted the Iran–Contra affair, where the US sold arms to Iran when the country was subject to an embargo. The justification of the sale was that it was part of an operation to free hostages in Lebanon. It transpired later that the proceeds of the arms sale were to fund a rebel group in Nicaragua.

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Ronald Reagan -

"A few months ago I told the American people I did not trade arms for hostages. My heart and my best intentions still tell me that's true, but the facts and the evidence tell me it is not. As the Tower board reported, what began as a strategic opening to Iran deteriorated, in its implementation, into trading arms for hostages. This runs counter to my own beliefs, to administration policy, and to the original strategy we had in mind. There are reasons why it happened, but no excuses. It was a mistake," said the president.

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George H.W. Bush -

George H.W. Bush regretted not managing to remove Saddam Hussein from power at the end of the first Gulf War in 1991.

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George H.W. Bush -

"If we had tried to get Saddam Hussein to come and literally surrender and put his sword on the table, I think it might have been avoided some of the problems that we did have in the future from him," said Bush Sr.

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George H.W. Bush -

George H.W. Bush also regretted lying to Americans. While campaigning in 1988, he promised: "Read my lips: no new taxes." As president, he failed to deliver on that promise and apologized for it in 1992, saying, “I did it, and I regret it and I regret it."

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Bill Clinton -

The thing Bill Clinton regrets the most is not ensuring peace in the Middle East. “My number one regret is that I was not able to persuade Yasser Arafat to accept the peace plan I offered at the end of my presidency,” he confessed.

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Bill Clinton -

"We'd be much better positioned to deal with the problem of Iran, and we would have taken away about half the arguments of terrorists around the world by giving the Palestinians their state and creating a cooperative, positive interdependence in the Middle East, not a negative one. And so, I think that would have done more good to save more lives and help more people, and I wish I had been able to do that," Clinton added.

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Bill Clinton -

Another thing Bill Clinton regrets is not doing more to stop the Rwandan genocide.

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Bill Clinton -

And, of course, Clinton also regrets the sex scandal with Monica Lewinsky. "I know that my public comments and my silence about this matter gave a false impression. I misled people, including even my wife. I deeply regret that," said the former president.

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George W. Bush -

When asked about his regrets in 2008, the former president made reference to the Iraq War. "The biggest regret of all the presidency has to have been the intelligence failure in Iraq," he said.

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George W. Bush -

Bush did share the blame with other world leaders who made decisions based on the same intelligence. "It wasn't just people in my administration; a lot of members in Congress, prior to my arrival in Washington, D.C., during the debate on Iraq, a lot of leaders of nations around the world, were all looking at the same intelligence.," he clarified. "I wish the intelligence had been different, I guess," added Bush.

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George W. Bush -

Bush also expressed regret about his response to Hurricane Katrina in 2005. "Katrina exposed serious problems in our response capability at all levels of government. And to the extent that the federal government didn't fully do its job right, I take responsibility," said Bush in a press conference.

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Barack Obama -

President Obama lists the way he handled Libya as his biggest regret. In 2011, Obama’s administration helped overthrow dictator Muammar Gaddafi from power, but failed to secure a plan for the future of the country.

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Barack Obama -

When asked about his biggest regrets while in office, Barack Obama’s response was: “Probably failing to plan for the day after what I think was the right thing to do in intervening in Libya.”

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Barack Obama -

In 2013, Obama also apologized to Americans who lost their health care plans due to the Affordable Care Act.

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Barack Obama -

"I am sorry that they are finding themselves in this situation based on assurances they got from me," he said. "I'm sorry my administration's policies really screwed these Americans," Obama added.

Sources: (CNN) (NPR) (BBC) (The New York Times) (Los Angeles Times) (Ranker) (Mental Floss)

See also: Surprising facts about all 46 US presidents

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