Justin Hammer is a rival business owner and millionaire to Tony Stark. He is one of Iron Man's enemies. He has no powers but has technology to use.
Marvel Cinematic Universe
Iron Man 2
Hammer is first seen when Stern called him to declare that the technology created by Tony is a risk to the United States. Hammer tries to discredit Stark showing US enemies trying to create their own armor but eventually is humiliated by Tony who shows a video to the public showing that Hammer also does the same thing.
Hammer meets again with Tony in Monaco, he is accompanied by the reporter Christine Everhart. When Tony tells her that Hammer lost the contract with the government she leaves him. Later, he is shown interested in the technology used by Vanko to attack Tony, then he sends him release from jail for help to discredit Tony. When he learns that Vanko doesn't comply as promised, Hammer gets mad and takes the pet of Vanko.
After James Rhodes steal one of the Tony's armor, Hammer is called in to improve it. Hammer weaponizes the armor with the best weapons of Hammer Industries. In Stark Expo, his presentation is interrupted by Iron Man, who knows that Hammer is working with Vanko. At that moment, Vanko takes control of the Drones to make these attacks against Tony and the public. Hammer with his technicians tries to take control of Drones but is stopped by Pepper and Natasha Romanoff, who obliged him to give the whereabouts of Vanko. Hammer is arrested after it was discovered that he freed Vanko from jail.
All Hail the King
In All Hail the King, Hammer is sitting beside a fellow prisoner and wondering what is so special about Slattery. Hammer says Slattery had no army of robots and also has a silly accent. At that time he is seen reading a Forbes Magazine with Pepper Potts on the cover.
Marvel Animated Universe
He also appeared in Avengers Assemble as a wannabe super villain. He created the robot Adaptoid Android to take on the Avengers. He also mined Vibranium in the Savage Lands and acquired an army of Raptors to fight the Avengers.