Richard Nixon. He concealed when he learned about the Watergate break-in, and resisted a wider criminal investigation. No one ever showed that he knew about it in advance, or that he benefitted from it.
Bill Clinton. He sexually harassed an intern, and lied about it under oath in a civil lawsuit.
Donald Trump. He asked Ukraine to investigate corruption with the Biden family, and possible held up arms aid for a couple of weeks. He also gave a speech on Jan. 6, 2021 suggesting follower protest peacefully to Congress.
Joe Biden. His son took bribes from shady players in Ukraine and China who were trying to buy influence with Joe. Joe denied knowing anything about it, and denied any responsibility to even find out. He also held up arms shipments to Ukraine, for political reasons.
I consider all of these offenses minor, compared to presidents who lied to get us into war, or who started wars without congressional approval, or who failed to protect our borders, or who violated the law to achieve some political end, or who wasted huge amounts of money, or who prosecuted political enemies on trumped up charges.
Democrats say that there is no evidence against Biden, but he covered up family bribery as much as Nixon covered up Watergate.