We know that at least two recent presidents committed felonies.
We have Richard Nixon, who Obstructed Justice as he tried to thwart the investigation into the Watergate burglaries. Nixon was also an Accessory After the Fact to those Burglaries, and he could also have been charged with Conspiracy as he was paying the burglars to be quiet. There are a whole slew of other crimes related to Watergate but those are the highlights for which Nixon could have been indicted
- When all of these facts came to light, Nixon resigned from the presidency, and was pardoned a month later (likely part of the agreement for him to go quietly).
We also have Bill Clinton, who in 1998 committed Grand Jury Perjury and Obstructed Justice when he lied about an affair in a sworn affidavit. Clinton was impeached for this lie, but Clinton was acquitted by the Senate.
- Subsequent to the acquittal, Clinton was cited for Contempt of Court and fined $90,000. Clinton was also investigated by the Arkansas bar and in a plea deal had his law license suspended for 5 years. Clinton also agreed to another plea deal with the special counsel Robert Ray paying a $25,000 fine to avoid indictments.
- Clinton could have quite easily been indicted once he left office had he not agreed to those plea deals. While opinions differ on whether Clinton got off easy or not for lying in a sworn affidavit about sex, a 5 year law license suspension is pretty hefty. Just consider, Jimmy McGill broke into his brother's house, destroyed evidence, and assaulted his brother, and Mr. Better Call Saul lost his license for just 1 year!
There are plenty of conspiracy theories, some of which I believe, about Ronald Reagan and George W Bush committing felonies, but there is no hard evidence about either. George HW Bush and Jimmy Carter kept their noses pretty clean, while Barack Obama avoided scandal like the plague during his stay in the White House.