The largest and most prominent collection of law enforcement agencies, including the United States Marshals Service; the Federal Bureau of Investigation; the Drug Enforcement Administration; the Bureau of Alcohol, Tobacco, Firearms and Explosives; and the Federal Bureau of Prisons, is the ______.

These agencies—including the FBI, DEA, U.S. Marshals Service, ATF, and Federal Bureau of Prisons—are part of the Department of Justice. The Department of Justice is the federal department responsible for enforcing federal law and administering the federal justice system, so the answer is Department of Justice.

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