Andrew Johnson, Bill Clinton, and Richard Nixon are the three U.S. presidents who were impeached by Congress. However, Andrew Johnson and Bill Clinton were acquitted by the Senate, while Nixon resigned before he could be impeached.
If you are asking which former U.S. president has not been impeached at all, many presidents fit that description, including Ronald Reagan, George H.W. Bush, George W. Bush, Barack Obama, Donald Trump (though he was impeached twice), and Joe Biden, among others.
In summary, there are numerous former U.S. presidents who have not been impeached, including those who served after Nixon, Johnson, and Clinton.
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