To hear him tell it in court, he has the blood of 78 people on his hands and allegedly shipped 20 tons of cocaine to the United States.
He also laundered millions of dollars, and, once imprisoned in America, started spilling the beans - and terrifying powerful people back home in his native Honduras.
From 2003 to 2013, Devis Leonel Rivera Maradiaga and his brother Javier, along with their parents and other siblings, led a violent drug cartel called Los Cachiros, in Tocoa on the Atlantic coast of Honduras, a country with one of the world's highest murder rates.
But the brothers feared getting killed when the US Treasury Department put the names of their whole family on a black list in 2013 and the government of Honduras began seizing assets from them.
So Leonel Rivera started secretly recording conversations with accomplices such as Fabio Lobo, son of former president Porfirio Lobo, who served from 2010 to 2014.
He did this first on his own and later in cooperation with the US Drug Enforcement Administration starting in 2013.
Leonel Rivera, who turned 40 on Tuesday, is a man of short stature with a thin moustache and arched eyebrows that make him look angry all the time.
Along with his brother he cut a deal with the US prosecutors in New York under which the pair landed in prison more than two years ago - but the rest of their family did not.
His mother, father, sister and a second brother live in the United States, presumably under a new identity and under the protection of the US government.
'A little window'
US authorities said this week that Leonel Rivera will be sentenced by Judge John Koeltl on April 14.
Thanks to his revelations, the authorities in Honduras learned that the Cachiros gang had at least 22 contracts with the Lobo government, prosecutors in Honduras said Wednesday.
They also said they would investigate the government officials named by Leonel Rivera.
"This is what makes the Cachiros case so interesting, because it's a little window into the way organized crime and elites intersect in places like Honduras," said Steven Dudley, co-director of Insight Crime, a think tank that studies organized crime in the Americas.
"This is important because it sends the message that impunity is not total, that there is some accountability somewhere, there exists some system that is willing to hold even the highest powers accountable," said Dudley.
"But does that transfer into real change? I am not sure yet."
From December 5, 2013 to September 21, 2015, Leonel Rivera met with US prosecutors 22 times to give them information and negotiate the terms of his plea bargain, according to court documents seen by AFP.
The two brothers surrendered to the DEA in January 2015, Leonel in the Bahamas and Javier in Miami.
In April 2016, they each pleaded guilty to charges including murder, leading a drug trafficking gang and conspiring to ship illegal drugs into the US.
The Cachiros gang took delivery of drugs from Colombia, which arrived either in planes or speedboats, and took it overland to Guatemala. From there it would move on to Mexico and then the US, Leonel Rivera said in his first testimony against Fabio Lobo on March 6.
He said that in exchange for bribes the cartel was protected by the former president, his son, his brother Ramon "Moncho" Lobo, the current Security Minister Julian Pacheco, by the legislator Antonio Hernandez, brother of President Juan Orlando Hernandez, and by dirty cops and military people.
All of these people deny the charges, except for Fabio Lobo, who was arrested by the DEA in Haiti in 2015. He has pleaded guilty to charges of drug trafficking and will be sentenced on May 30.
'Deal with the devil'
If convicted Leonel Rivera could face life in prison but his fate depends on judge Koeltl.
His plea bargain, signed April 14 of last year, calls for the charges against him to be dropped if he tells the truth, does not commit more crimes and testifies when the government asks him to.
The US government could also grant him a so-called "5K1" card that calls for a reduced sentence and perhaps entry into a witness protection program.
"It's the deal with the devil," said a lawyer close to the case. "This guy has admitted to 78 murders" but the judge has complete discretion when it comes to deciding on his sentence.
In theory, "he could walk out of his sentence" meaning walk out of court and start life anew with an assumed identity, the lawyer said.