Joaquin Garcia spent 24 of his 26 years with the FBI working undercover . "I've done over a hundred undercover investigations," he told Business Insider. His investigations spanned the Italian Mafia, Mexican and Colombian cartels, Russian and Asian organized crime groups, police corruption rings, jury bribery schemes, murder-for-hire setups, and large-scale narcotics operations. Of all the criminal organizations he infiltrated , Garcia fears one above the rest. "Mexican cartels are just simply