Sergei Vladimir is the main antagonist of Resident Evil: The Umbrella Chronicles. A former colonel in the Soviet Union army, he was hired by Oswell E. Spencer following the Union's collapse and became the Commander-in-Chief of Umbrella's paramilitary forces. Eternally grateful to Spencer, Sergei became the Umbrella founder's right-hand man, taking orders directly from him. He also formed a rivalry with another of Spencer's lieutenants - Albert Wesker.
The Tyrant Project
During his time with Umbrella, Sergei became instrumental in the development of the Tyrant Project, recognised as a perfect candidate for Tyrant development. Since only one in ten million humans possessed the potential to become Tyrants, Sergei allowed Umbrella to use him as a genetic template to produce the T-103 models, creating ten clones of the colonel to use for the weapons' development. Two such Tyrant models were modified and programmed to follow Sergei's direct instructions, becoming his own personal bodyguards - Ivan.
The Red Queen
At the Umbrella Research Center, Sergei ordered one of his Ivans to "punish" Wesker for his failure to bring the facility up and running. Wesker barely escaped with his life, with only the destruction of the facility giving him a chance to escape, causing Sergei to say "I guess he didn't like his lesson". Afterwards, Sergei and his bodyguard went to the Arklay Mountains Spencer Mansion. Rebecca Chambers quietly watched him exit the mansion alongside the Ivan carrying the T-A.L.O.S. prototype. They were attacked by a group of Cerberus', but the Ivan easily dispatched them. Sergei was then sent to Raccoon City to retrieve the U.M.F.-013 computer core, which Sergei had loaded all of Umbrella's data onto.
Sergei saw himself going down in history as a hero because of the last task Oswell E. Spencer had left him with. After Raccoon City's destruction, the government got suspicious of Umbrella and its position in the world was dwindling, making it a sinking ship and no longer a sanctuary for his plans. Spencer had no choice but to further distance himself from the public eye, which he had never stayed close to in the first place. However, before going into hiding, Spencer needed someone to take charge of what was left of his corporation. He chose Sergei, his most faithful and loyal subordinate, confident he would be able to uphold the seemingly doomed company. Sergei was named the chief executive officer of Umbrella some time between 1998 and 2003. It is likely the two still maintained contact behind the scenes. As his first decree as Umbrella's leader, Sergei moved all company data and assets to the Caucasus facility disguised as an oil refinery.
The Fall of Umbrella
Wesker himself infiltrated the Caucasus base at the same time a biohazard wiped out some 98% of the research staff. Wesker managed to take a train to the main shaft where he met Sergei a second time. This time, Sergei sent both of his Ivans to kill him. An attack team lead by Chris Redfield and Jill Valentine entered the base, with the intention of destroying Umbrella for good. None of that would have been possible if it was not for Wesker's actions.
Sergei stood in the way of Wesker's attempt to steal the U.M.F.-013's data and, after releasing the T-A.L.O.S. to fight Chris and Jill, he mutated into a huge Tyrant-like creature (indication that he infected himself moments before Wesker caught him). The tentacles binding his arms fused into one large tentacle. At the end of this appendage is a dangerous claw that can be used for movement or attacking.
During the fight, Sergei seemed to enjoy the blows of pain Wesker issued to his weak point, evidencing a loss of sanity. Despite Sergei's immense strength, agility and organic weaponry, Wesker destroyed him, putting an end to his delusions that Umbrella and the Tyrants, his "brothers", would usher in a new era for mankind. The company's final leader defeated, Wesker stole all of the data, compressed into one disc, and shut down the Red Queen. The base was decommissioned and all data was erased in the process, ending Sergei's plans and sealing Umbrella's fate.
Before his mutation, Colonel Vladimir was an experienced combat veteran and a brilliant strategist. He always carried an exotic double-edged blade which he could likely wield to great effect, though in Umbrella Chronicles he is only seen using it to cut himself. While not as great a scientist as others within the Umbrella Corporation, Sergei did possess a keen intellect and made significant contributions to the company's B.O.W. research, most notably the Tyrant series.
When Sergei injected himself with the T-virus, he transformed into a grotesque creature. His arms fused together into a long tentacle ending in snapping mandibles. He also grew a number of smaller barbed tentacles out of his back which he used to attack and cling to different surfaces. His most impressive power, however, was the ability to spawn organic projectiles that he could launch at opponents. Like the Tyrants, Sergei's mutant form also possessed accelerated healing, offering him great resistance to most weapons.
Sergei's mutant form has an exposed vascular organ which provides a significant weak spot. However, after receiving so much damage during his battle with Wesker, his healing factor increased and made him invulnerable to virtually all weapons apart from high explosives. Wesker was only able to finish off Sergei with a rocket launcher and upon his death, Sergei's body rapidly deteriorated, melting away into nothing.