Matt Addison is the deuterogamist of the first Resident Evil film. He is also the (former) secondary antagonist in Resident Evil: Apocalypse when appearing as the mutant killing machine called "Nemesis".
In the first film, Matt (portrayed by Eric Mabius) is a member of an unnamed group of environmental activists working to expose the illegal activities of the Umbrella Corporation, the world's leading pharmaceutical giant. His sister Lisa is also a member of this group and she infiltrates Umbrella's underground Hive complex after the corporation hires her as a systems analyst. After losing touch with Lisa, Matt goes undercover as a Raccoon City cop to investigate the Arklay mansion, an Umbrella front to hide the emergency entrance to the Hive. Just as Matt begins investigating, he is interrupted by Umbrella Special Ops soldiers dispatched to shut down the Hive's main computer, The Red Queen. The commandoes take Matt with them, keeping him handcuffed as they explore the strangely empty facility.
After the Red Queen is shut down, all the doors in the Hive are opened and the facility staff - who have all been turned into zombies by the T-virus - escape. A firefight ensues down in the "Dining Hall" and Matt manages to grab the key to his cuffs and frees himself. He then goes looking for his sister Lisa, who he finds in her office and also infected with the T-virus. Alice - the main protagonist - saves Matt from being bitten and kills the zombified Lisa. Afterwards, Matt explains the truth about himself and his group to Alice and how they planned to steal the T-virus and expose Umbrella to the press.
Near the end of the film, Matt, Alice, Kaplan and Rain are on the train headed out of the Hive, with a mutated Licker in hot pursuit. As the monster tears into the train, its claws scratch Matt's shoulder and pass on the T-virus. Minutes later, Alice and Matt are the only two to escape before the Hive closes, and as they arrive back in the mansion, Matt doubles over in pain. Realising he is infected, Alice prepares to inject Matt with the antivirus, but is stopped when a group of Umbrella personnel in hazmat suits enter the mansion and take the two survivors away. As the two are separated, an Umbrella scientist notices small tentacles emerging from Matt's shoulder wound and states "He's mutating. I want him in the Nemesis Program." Matt is then carted away and Alice never sees him again... at least, not as a normal human.
Resident Evil: Apocalypse
In the second Resident Evil film, Matt is no longer human, having been transformed by Umbrella into their ultimate bio-weapon: the unstoppable creature called "Nemesis". Nemesis is portrayed by Matthew G. Taylor and the character's appearance and abilities resemble those of the Nemesis monster from the Resident Evil video games.
After being taken away by Umbrella, Matt - who had begun to mutate after being wounded by a mutated Licker - was subjected to horrific experiments and surgically and genetically augmented to become a super-strong bio-weapon commando. Matt - now codenamed Nemesis - had a computerized control device implanted in his brain, allowing Umbrella to dictate his actions and see through his eyes. During the T-virus outbreak in Raccoon City, Nemesis was deployed to test its capabilities. It was supplied with heavy weaponry - a rocket launcher and a minigun - and sent out to exterminate the remnants of Raccoon City's police and special forces. Matt's consciousness remained surpressed and could not control his actions, though he was apparently aware of them.
Nemesis would later encounter its primary target: former Umbrella agent and special test subject Alice. It pursued her through the streets and into a building, but would break off pursuit after Alice slid down a laundry chute, which the monster could not fit through. It would re-encounter Alice and other survivors of the disaster at the heliport on top of city hall, where Umbrella's paramilitary chief Major Cain commanded it and Alice to fight one on one. Though Nemesis had discarded its weapons, during the fight it tore off a jagged piece of metal from a pylon on the roof, brandishing it like a makeshift sword. While not physically as strong as Nemesis, Alice made up for it with her superior speed and reflexes. She battered at the creature and backed it up against the pylon it had torn a piece from, kicking it in the chest and impaling it on a jagged piece of protruding metal. At that point, Alice's jaded memory fully cleared and she recalled what had happened to Matt Addison. Realising that the Nemesis was Matt, she sobbed and apologised profusely. This stirred something within Nemesis and allowed Matt's consciousness to regain control of his body.
As Cain ordered his remaining troops to evacuate, he commanded Nemesis to kill Alice. Matt, once again in control of himself, picked up his minigun and opened fire on the Umbrella troops. The troopers fought back but their weapons were useless against Matt's super-powerful mutant form. As two Umbrella attack choppers tried to kill Alice, Matt stepped in front of Alice and raised his rocket launcher at the aircraft. Both choppers were shot down and Matt shoved Alice out of the way as the flaming wreck of one chopper crashed on top of him, crushing him to death.
In the novelisation of Resident Evil: Apocalypse, it is suggested that Matt may have survived the helicopter crashing upon him. However, Matt surely would have died when Raccoon City was obliterated by the nuclear missile that had been launched by an Umbrella craft just as Nemesis turned on its masters.