James Joseph "Whitey" Bulger Jr. was an organized crime leader in Boston from the 1960s through the 1990s.  He went into hiding in 1994 and wasn't found and arrested until 2011, resulting in him sitting behind only Osama Bin Laden on the FBI's ten most wanted list.  Most astonishingly, Bulger managed to operate as an FBI informant during his career.  By giving information on his rivals and being shielded from arrest by his status, he managed to become one of the most powerful organized crime bosses in America.