Fred Duncan is a fictional character in the Marvel Universe

Marvel Universe

The Marvel Universe is the shared fictional universe where most comic book titles and other media published by Marvel Entertainment take place, including those featuring Marvel's most familiar characters, such as Spider-Man, the Hulk, the X-Men, and the Avengers.The Marvel Universe is further...

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Frederick Amos "Fred" Duncan was an agent with the FBI

Federal Bureau of Investigation

The Federal Bureau of Investigation is an agency of the United States Department of Justice that serves as both a federal criminal investigative body and an internal intelligence agency . The FBI has investigative jurisdiction over violations of more than 200 categories of federal crime...

. He met with Professor Charles Xavier

Professor X

Professor Charles Francis Xavier, also known as Professor X, is a fictional character, a Marvel Comics superhero known as the leader and founder of the X-Men....

 and became the FBI's federal liaison with the X-Men

X-Men

The X-Men are a superhero team in the . They were created by writer Stan Lee and artist Jack Kirby, and first appeared in The X-Men #1...

. As a member of the Xavier Underground

Underground (comics)

The Underground was a short-lived team of superheroes in the Marvel Comics universe. They appeared in the comic-series Weapon X.-Fictional team biography:...

, a network of mutant supporters, Duncan maintained mutant criminal records and stockpiled weapons and technology from X-Men foes. After Duncan's death, Carl Denti, an aspiring agent, takes the files, weapons, and technology for himself and assumes the name X-Cutioner

X-Cutioner

The X-Cutioner is a fictional character appearing in the Marvel Comics universe. He is a former FBI agent obsessed with stalking Mutants who kill humans, and uses an array of both alien technology and Earthly technology in his quest...

, with the proclaimed mission of killing any mutant that has killed other people first.