For over a decade, Michael Cohen has been Donald Trump’s personal attorney. As such, he probably knows more about Trump’s business dealings, numerous extramarital affairs, and connections to questionable people than anyone else. And that’s a big problem for the president now that Cohen is pleading guilty.

What, you may wonder, does Cohen know that’s so dangerous to Trump? When it comes to collusion/conspiracy with Russia, Cohen has enough evidence to put Trump away for the rest of his life. As Ryan Goodman wrote on Just Security, Cohen can tell Robert Mueller and the U.S. Attorney’s Office in New York:

“If Cohen was in frequent contact with individuals who had knowledge of or played a role in the 2016 election interference, it would corroborate some aspects of the Steele Dossier. That report, compiled by former British intelligence officer Christopher Steele, suggested that Cohen may have played a central role in the coordination between Russia and the Trump circle.”

The Steele dossier is also the same document that alleged Russia had compromising information — i.e. the infamous “golden shower” tape — on Trump, and Cohen may also be able to verify the existence of such tapes and other damaging information Vladimir Putin has used to control the president. That alone would prove a motive for why Trump has been so deferential to the Kremlin and refuses to say anything negative about Putin.

And let’s not forget about those payments to women Trump allegedly slept with and later paid to keep quiet. John Cassidy of the New Yorker notes:

“Cohen may provide information about payoffs that he made on Trump’s behalf to women who claimed to have had affairs with the President. We know about the payment of a hundred and thirty thousand dollars that Cohen made to Stephanie Clifford (a.k.a. Stormy Daniels), of course. But Rudy Giuliani, Trump’s lawyer and cable-news pit bull, has publicly indicated that it is perfectly possible that Cohen paid off more women before the 2016 election.”

Those payments were made under the guise of a shady corporation Cohen created in Delaware. Problem is, in doing so, Cohen likely broke numerous banking, fraud, and campaign finance laws.

The business side of Trump’s life is also ripe for possible criminal activity. How much money has he taken from Russian sources, and did he launder money for Russian oligarchs? If so, Cohen would know all about that, too.

Cohen is the most dangerous man in the world to Donald Trump. He knows, as the old saying goes, where all the bodies are buried, and who put them there. That alone makes him an enormous existential threat to the president.