Aladena “Jimmy the Weasel” Fratianno was a longtime Mafia hit man and Los Angeles mob boss before turning into an FBI informant. After turning informant, he spent most of his time traveling the country to testify against fellow mobsters and becoming the highest-paid participant in the history of the federal witness-protection program. Life in retirement did not always go smoothly, as he sued his hand-picked biographer of his first book, “The Last Mafioso,” saying it contained false quotes. He blamed the second, “Vengeance Is Mine,” for his being dropped from the witness program’s payroll in 1987. Fratianno gained his nickname from running “like a weasel” from a pursuing police officer, though, like Benjamin “Bugsy” Siegel, he was seldom called it to his face.

You can read more about Jimmy the Weasel here: https://themobmuseum.org/blog/jimmy-weasel-fratianno-government-witness-mob-family/