He is portrayed by Benicio Del Toro, who also played Dario in License to Kill, The Collector in the MCU, Jack Rafferty in Sin City, Lawrence Talbot in the 2010 remake of The Wolfman and DJ in Star Wars: The Last Jedi.
Hallam is a former student of L.T. Bonham, a trainer of military assassins, but went rogue after suffering from severe battle stress from his time spent fighting in the Kosovo war. After committing two murders, Hallam is apprehended by the authorities who convince Bonham to join them in their search. Bonham locates Hallam at a forest den he had been living in, and they fight. The authorities then move in and successfully capture Hallam before interrogating him. Hallam claims that he is under threat from the Army due to unofficial assignments he had previously been involved in, and soon enough various government agents arrive with proof that they may take possession of Hallam. As Hallam is being driven away by the agents, he strangles one of them with his chains and causes the van to crash. With all the agents dead, Hallam escapes unharmed.
Bonham hears news of the crash and immediately travels to the scene along with the FBI. Bonham tracks Hallam at his old house where his former partner is still living, but Hallam escapes through a window and Bonham is forced to give chase. Hallam kills another agent and boards a moving train in hopes of evading Bonham, but Bonham also climbs aboard and confronts Hallam in one of the carriages. As the passengers flee in panic, Hallam climbs onto the train's roof before clambering up to the top of a bridge high above Bonham and the FBI team. As a police helicopter hovers above him, Hallam leaps into the waters below and is quickly swept downriver by the strong current.
Bonham follows the river to a national forest with waterfalls and white water rapids, where Hallam is waiting for him. The pair engages in another brutal fight, during which Hallam almost kills Bonham by slashing him continuously with a knife. After an intense battle, Bonham grabs Hallam's knife and kills his former student by stabbing him in the chest. The FBI team arrive just as Hallam dies.
- Aaron is similar to Rambo from First Blood the novel, which The Hunted is considered to be an unofficial adaptation of.
- Benicio Del Toro broke his wrist while filming a fight scene with Tommy Lee Jones, halting production for four months and pushing back the release date.