Corporal Dean Portman is a member of the Rapid Response Tactical Squad and the antihero of the 2005 film Doom.
A borderline sociopath, Portman is shown to be a ribald wisecracker with a warped, sadistic sense of humor, and is hated by most of the group. He is first seen discussing his plans when he goes on his leave. When the group arrives at the Olduvai Research Facility on Mars, Portman seizes the opportunity to sexually harass five female UAC employees, including Reaper's twin sister, Dr. Samantha Grimm, moments before Portman is first paired with Goat.
After searching through the Genetics Laboratory, the two discover a large pit that turns out to be a holding cell. When Goat tells Portman to touch the walls of the cell, he gets shocked by the electricity. Portman is then paired with The Kid after the group finds Dr. Todd Carmack alive. Portman begins to taunt The Kid about Dr. Carmack ripping off his ear, which makes The Kid feel uneasy. At The Kid’s urging, Portman gives him some narcotics to calm down.
While searching through the air lock, Portman walks upon a naked woman much to his excitement. When The Kid tries to grab her attention, he and Portman shoot her multiple times after she tries to attack them. Portman looks down at the woman’s corpse and realizes she is one of the missing scientists when he notices her severed arm. After the group reunites near the entrance of the sewers, Portman is initially hesitant to go down. Whilst searching for Dr. Steve Willits, Portman nearly drowns after falling through a hole in the water. Portman is audibly shaken by the discovery of a mutated creature, believing it to be an alien. Portman refuses to go back in the lab complex after Goat is killed. Portman reminds RRTS leader Sarge that reinforcements should be called in when a threat is great enough. He suggests they do so, only to be rebuffed by Sarge.
Shortly afterwards, Portman is paired with Destroyer and the two guard the door that separates the Arc chamber from the quarantined area. Portman feels the urge to go to the bathroom and leaves Destroyer to guard the door alone. In reality, Portman actually went to the bathroom so he can send an emergency distress signal requesting reinforcements without getting in trouble. After Portman sends the transmission, he begins hearing strange noises and becomes paranoid that something is lurking nearby. While changing an empty magazine in his gun, Portman drops the clip which slides under several stalls. Portman crawls under the stalls and eventually retrieves the clip. He then comes out of the stall and sees a mouse crawling away, believing that he got worked up about nothing. But Portman is then dragged through the ceiling by an Imp, who proceeds to violently bash his body through the walls. This barbarity is witnessed by Marcus Pinzerowski through Portman's gun cam and does nothing to save his life as retribution for Portman insulting him earlier. Eventually, Portman's neck is snapped by the bashing and dies before the Imp drops him to the ground. When the RRTS finds Portman's body, The Kid confirms his death by checking his pulse.
Portman’s body is taken back to Samantha's laboratory for an autopsy. The group does not learn of the transmission sent by Portman until they return to Earth.