Mikhail Victor was a Russian lieutenant in the UBCS sent into Raccoon City by Umbrella. After only a few hours of fighting against the army of zombies, Mikhail's unit was whittled down to himself, Carlos Oliveira and Nicholai Ginovaef. By the time the three met up with former STARS member Jill Valentine, Mikhail was severely wounded and half out of his mind from bloodloss.
Although initially Mikhail saw himself as merely a burden to his friends, when Nemesis appeared to kill Jill as he'd been programmed to by Umbrella, Mikhail (who, like Carlos, had no love for Umbrella), came to her aid. He covered her and Carlos' escape, sacrificing himself in a heroic by ultimately fruitless attempt to kill the monster by detonating a grenade when Nemesis was close enough. The force of the blast killed Mikhail, and although it did not kill Nemesis, it stunned him long enough for Jill and Carlos to escape.
Nicholai shot Mikhail in an early attempt to kill him, as part of his plan to be the only survivor of the UBCS.