Two, almost three, presidents have been impeached in my lifetime: The two are Bill Clinton and Donald Trump. One other president was on the verge of being impeached but resigned first: Richard Nixon. All three of them have been accused of dishonesty. As I recall, Bill Clinton was described as either having "lied to the American people" or having "lied under oath", or both (done together as one event).
The impeachment of Bill Clinton made much of that. He was placed under oath when he testified before the Senate in his impeachment hearing(s).
Probably all presidents have been bad in one way or another, if only because they failed in the Herculean task of reforming some of the bad things. But one of the most explicit and official examples of OBJECTING to p**********l bad behavior was in the Clinton impeachment in which some officials acted like they REALLY cared that he lied under oath or "lied to the American people". That seemed to be the one most major thing the impeachment hinged on.
There are a couple of other presidents whom I'd add to the list of presidents under consideration: Ronald Reagan and George W. Bush. Some of you are probably familiar with what people think _they_ did wrong. (In the case of Reagan, people didn't talk about him directly so much as about what happened in his Administration -- more focus was on people like Oliver North.)
Impeachment is not the only indication that something may be seriously wrong. Maybe all presidents are bad, but I invite you to choose one of the above five presidents as a bad one.
Now, regarding _any_one_ of those five presidents:
1. Did he deceive or mislead anybody important -- the American people? -- Congress?
2. If he did, then did it matter? Was it important enough that we should care about it?
3. Was there something harmful about what he did? Again, is it important enough that we should care about it?
4. Did it have to happen that way? Was it just par for the course? Or did it really make things significantly worse, that the president said, did, failed to say, or failed to do, as happened? Was the president "at fault" or "the wrong person for the job"?
Audio and text of what one of those presidents knew and said are found at the following link:
https://www.npr.org/2020/09/10/911368698/trump-tells-woodward-he-deliberately-downplayed-c****av***s-threat