Plot

Special Agent Leon S.Kennedy goes against his superior's orders and works to destroy a series of biological weapons being used in a war zone in Europe.

United States Special Agent Leon S. Kennedy sneaks into a small Eastern European country to verify rumors that Bio Organic Weapons (B.O.W.s) are being used in war. Right after his infiltration, the U.S. government orders him to leave immediately. Determined to uncover the truth, Leon ignores the order and enters the battlefield to end the chain of tragedies caused by the B.O.W.s.—KalantarAhUra

Special Agent Leon S. Kennedy comes face-to-face with a nightmare he may never be able to escape as the terrifying Resident Evil saga continues. Convinced that Bio Organic Weapons (B.O.W.s) are being used in combat, Leon} infiltrates a secluded Eastern European seeking the evidence he needs to confirm the rumors. As soon as Leon crosses the border, however, his contacts in the U.S. order him to abort his mission immediately. But he's come too far to simply turn his back now, and as Leon vows to neutralize the threat of B.O.W.s once and for all, the Umbrella Corporation's most dangerous weapon threatens to unleash a literal hell on earth.

WARNING: This is a detailed summary of the events of which happened within the film. If you have not seen the film but do wish to, I would strongly advise that you not read ahead as it will be chock full of spoilers. Read at your own risk.

The film begins with the character Buddy narrating over the opening titles the events of civil war within the Eastern Slav Republic following the dissolution of the Soviet Union. The corrupt female president Svetlana Belikova has been gaining the upper hand as of late which has prompted the rebels led by Buddy to resort to Bio- Organic Weapons (BOWs) weapons. With news like that, Leon S Kennedy sneaks into the Eastern Slav Republic. Upon arriving, he is met by a message sent by his mission support Ingrid Hunnigan who tells him that the government has ordered an immediate evacuation of all American forces. Leon, having come this far, refuses to leave with Bio weapons on the loose. He gets rid of his phone and goes against orders, traveling further into the city streets. He comes across his contact "Scarecrow" in a parking garage, seeing that he is mortally wounded. Despite trying to help Scarecrow, Leon is attacked by a Licker who kills Scarecrow and pursues Leon. Leon is almost killed when an explosion throws him unconscious but is spared when a shadowy figure controlling the beast via mind control, orders the Lciker to stop.

Leon awakens a captive to three "Freedom Fighters" rebel leaders JD, Buddy, and the aged and ill Ataman, Ivan Judanovich. JD takes a mild liking to Leon and expresses a liking for American products while Buddy remains calm and cold, and Ivan hacks and coughs violently. As this is going on, President Belikova calls a meeting with Ada Wong, posing as a BSAA agent. Ada explains how a master-slave relationship between a human and a BOW via the virus dominant strain. Elsewhere, Leon, JD, Buddy, and Ivan are attacked by Belikova's forces, but they are distracted when Ivan begins showing signs of undead characteristics. JD and Buddy manage to kill the forces and escape dragging with them the infected and dying Ivan. Leon eludes them but overhears Ivan telling Buddy to kill him as he is no longer in functioning condition and will turn. Leon overhears Buddy reluctantly shooting Ivan to death with disgust.

JD and Buddy become separated and Leon finds JD, rescuing him from several infected rebels who have turned and become Plaga hosts. These creatures pursue the two throughout the sewers until Leon and JD barely escape to the exterior city streets. They then witness in shocking horror a soldier being forced to his knees by the Infected and a transformation spore is forced painfully down his throat. JD leads Leon to a church where the rebels are hiding out.Leon tries to reason with Buddy, who plans to use the Plaga for the battle's use but Buddy rebuffs his advice. After Buddy leaves, JD helps Leon escape after telling him of Buddy, and how he was once a pacifist who became a rebel when the Russian government bombed a school he worked at mistaking it for a rebel hideout. The explosion had killed Buddy's wife, and turned him to take up arms. Leon leaves to stop Buddy, just as infected began surrounding the church.

Leon reaches the place Buddy entered only to find it abandoned with the strain taken by Buddy. He is confronted by Ada and assumes that she is responsible due to the sample retrieval mission in "Resident Evil 4" which she denies but confesses to retrieving a sample in Eastern Slav. She flirtatiously asks Leon if they are ever going to continue "that night" to which Leon replies "Anytime but now." Ada warns Leon that the place will be purged soon by Belakova's forces before escaping into the night. Leon rushes back to the church to see all the rebels overcome by the infected and JD as the remaining survivor, though mortally wounded and infected. JD gives Leon his weapons and armored vest right before Buddy arrives. As JD begins to turn, he confesses to Buddy that he was never in the fight for just freedom, but mainly to hang out with his friends, right before his head bursts into tentacles. Leon shoots him to death feeling bitter about it.

Leon tries once more to convince Buddy not to use the virus, but Buddy refuses and escapes just as the church is jet bombed and the ceiling caves in, with Leon narrowly escaping. The next day, Belakova digs deeper and discovers that Ada is a fraud and is after a virus. Belekova confronts Ada about this while having tea and Ada attacks her. The two women frighting hand-to-hand combat to a draw with Belakova seemingly gaining the upper hand. However, they are distracted by gunfire outside. Ada takes this opportunity to escape but is trapped in a sealed room the believed was an elevator. Buddy attacks the capitol with a team of Licker lackeys which make short work of Belakova's soldiers. Leon breaches the capitol walls and is set upon by them. He manages to escape and meets up with Ada, who had found herself tied up but had freed herself with a knife strapped to her thigh.

The two stumble upon the main hive control and discover what Belakova was really working on, before being confronted by Belakova and a squadron of her soldiers. However, Buddy and his lickers arrive and attack. Ada escapes but Leon and the soldiers are set upon by Buddy.Leon asks Buddy if he used the strain, fearing and already knowing the answer. Buddy sics a licker upon him but Leon manages to shoot it dead, despite getting his vest cut open. Leon then sees JD's flask sticking out of it and sighs saying, as if to JD, "I'm sorry, I couldn't stop him" before taking a drink from it. Leon tries to shoot and kill Buddy, but Buddy eludes him and Leon is chased by more lickers as Belakova's men are killed off.

Buddy attacks Belakove who takes refuge safely behind an impenetrable glass barrier. Belakova sets out her own BOWs, the Tyrants upon Leon and Buddy who now take up an unlikely alliance. Belakova escapes to make a faux report of propaganda while Leon and Buddy flee outside, pursued by a persistent Tyrant. Buddy distracts the giant with lickers long enough for Leon to shoot a nearby petroleum truck, seemingly destroying the beast. However, the Tyrant steps out of the fire an smoke, unfazed by the explosion. The now naked Tyrant attacks Leon and smashes him against the column on the steps of the capitol. Leon tries to fight back but finds that his gun is empty. As the Tyrant prepares to kill Leon, Buddy commandeers a tank and collides with the Tyrant. Leon hops in the back of the tank and with great effort, manages to blow the Tyrant's head off, killing it indefinitely.

The tank drives over the Tyrant's corpse and flips over. As Leon and Buddy crawl out, Leon asks Buddy if he's up for a few beers. Buddy replies only if Leon is buying. Giving into the painful effects of the infection, Buddy sees two more musclebound Tyrants approaching them and insists Leon leave him behind. Leon refuses and carries Buddy off with him as the Tyrants chase after them. Meanwhile, Belakova is beginning her address to the nation only to be informed by her aide that the Americans and Russians have arrived and are attacking. Buddy and Leon limp to a nearby water fountain where they find themselves surrounded by the Tyrants. Leon finds he is out of ammunition and brandishes his combat knife, preparing for a last stand. Just then, a USAF 10 attack plane arrives and tears apart one of the Tyrants with heavy gunfire and blowing up the other. Leon realizes that the Americans were keeping tabs on him the entire time.

A disappointed Leon, leans on the rail of a nearby bridge and watches the battles take place as Buddy sits behind him, depressed. Buddy states he has nothing left to live for, having lost his wife, his mentor, and all of his friends, and will become a monster soon. Buddy begs Leon to kill him so that he will not turn but Leon silently refuses. Buddy prepares to shoot himself but Leon snatches the gun away, stating that there is and needs to be something to live for, and that enough people have died. He then raises the gun, telling Buddy goodbye, before shooting him.

3 days later one morning, Leon is shown in his hotel room, drinking, which is much unlike him. He is watching the news and talking with Hunnigan about the mission. Leon is still disappointed that the outside forces of the US and Russians did nothing to prevent these disasters before and were mainly out for their own self-interests, not intervening until the last minute. Hunnigan insists that good had been done but Leon coldly hangs up before saying, "In the end, nothing really changes." Leon leaves the room to clear his head of this ordeal. Elsewhere, a cleaned up and reformed Buddy is shown in a wheelchair. It is revealed that Leon had shot him in the spine to prevent the strain growth. Buddy painfully, but happily pushes his wheelchair up the street, having become a teacher once more and finding something to live for.

In a post credit scene Ada speaks with her employer about a Plaga sample she retrieved earlier but haggles it, explaining she is unsure what to do with it. Her employer removes a universal arrest warrant on her, to which she is impressed by, but still hasn't quite made up her mind on the matter before signing out. The end credits roll alongside footage from the video game "Resident Evil 6." The title "Resident Evil: Damnation" appears in a dark screen one last time before fading away.