- "I'm not afraid of John Wick!"
- —Iosef Tarasov before John Wick starts hunting him.
The secondary antagonist in the 2014 film John Wick, Iosef serves as the primary target of the titular protagonist after the former assaulted Wick and killed his dog. These actions against John triggered the chain of events during the series.
Iosef is the only known child of the Russian crime lord Viggo Tarasov, and is involved with his father's organization.
Iosef begins his involvement in John Wick's story by meeting him at a gas station with his friends Victor and Gregori; he admires Wick's car (a Mustang 69), banging on the hood before ignorantly asking how much he wanted for it. John states that the vehicle isn't for sale, to which Iosef responds in Russian, "Everything's got a price, b*tch". Upon hearing John's response (similarly in Russian), "Not this b*tch", Iosef seemingly becomes irritated, leaning into the car before being pulled away by Victor.
At night, Iosef, Victor and Gregori proceed to break into John's house, where they beat up John and steal his car, right after Iosef kills John's pet puppy Daisy. John is horrified by this because Daisy was the last present of his deceased wife and angrily vows to avenge his dog's death by killing Iosef.
Iosef, Gregori and Victor later brought the Mustang to a mechanic named Aurelio and try to have the car modified but Aurelio questions Viggo's son about who and where he stole it from. Iosef is oblivious to the danger he is currently faced with and does not hesitate to mock Aurelio, stating that the Tarasov Mob owns his company. Aurelio asks Iosef whether or not he killed John before punching him in the face upon hearing that they had not only left him alive, but also given him reasons to come after them. Aurelio demands that they leave his shop — Iosef complies, but not before threatening him.
- "Iosef Tarasov: Are you scared of the fucking boogeyman? I'm not.
Kirill: No? But you should be."
- —Iosef Tarasov and Kirill.
As such, Viggo angrily berates Iosef in the gang's HQ for provoking John and punches him twice in the stomach for it, but Iosef refuses to care, attempting to convince his father to give him a chance to finish off John only to be swiftly dismissed and warned by Viggo that the boogeyman will eventually come for him and kill him. Viggo initially attempts to reason out John out of getting revenge but to no avail in which the latter silently refuses which leds to Viggo in sending his 12-man hit squad to John's house to kill him only for John to successfully eliminate Viggo's 12-man hit squad, which resulted to the Russian mobster in placing a bounty on Wick's head, which caused some of the Continental Hotel's assassins to hunt down John, amongst them being Marcus and Ms. Perkins. Meanwhile, Viggo had Iosef secured at his nightclub, the Red Circle club with his chief of security, Kirill, and his henchmen protecting him.
At the club, Iosef and his friends party in a hot tub before Kirill arrives to serve as his bodyguard. Iosef states him that despite the imminent threat, he is not afraid of "the Boogeyman". Kirill reminds him that he should be, a statement that is proved to be true by Wick himself as he bursts into the club, forcing Iosef to flee and thereby revealing his fear. He escapes the club in nothing but a bath towel, phoning Victor only to be answered by John, who reminds him of his previous statement, "Everything's got a price".
- "It was just a fuck'n-"
- —Iosef's last words before John Wick executes him
While holding Viggo at gunpoint, John learns that Iosef is hidden in a safe house in Brooklyn and takes out Gregori, Ivan and all of the guards. Alexander and another bodyguard attempt to flee with Iosef by car, but the two are shot and the cars are blown up. A terrified Iosef tries to run but gets shot in the stomach. Injured, he sinks to the floor while John approaches. Iosef tries to save himself by convincing John that it was "just a f-ckin' dog" he just killed, but the hitman angrily ignores this and instead shoots Iosef in the head, killing him and avenging Daisy's death for good.
Iosef was prideful, headstrong, vain, and exceptionally petty and cruel. His relationship with the Tarasov Mob, especially given that his father was the leader of the group, lead him to become spoiled and overindulgent, though he is shown to be entrusted and competent to an extent with his duties to the Mob. When Viggo described John to him, he offhandedly implied that Iosef was weak-willed, unfocused, and incapable of commitment.
Eventually Iosef's pettiness and cruelty would ultimately lead him to crossing John, unaware of the latter's previous association to the Mob and his father, and how incredibly dangerous John was. Though initially believing he can take on John, he was quick to lose this notion upon Viggo making it clear to him how serious the situation was. Over time, Iosef was shown to be more and more frightened and cowardly during John'S pursuit of him. But as John finally caught up to him, Iosef seemed to resign himself to his fate, expressing no remorse for his actions just before being executed by the former hitman.
- Combatant: As the pampered heir to the Tarasov fortune, Iosef has little combat training, never once fighting fairly but rather picking on those that he can (such as a prone John Wick during the Break-In). His fear also becomes evident during combat situations, using a bystander as a human shield while fleeing the Red Circle club.
- Iosef is widely considered to be the most hated villain in the John Wick series due to him killing Daisy, which was John's last gift from his deceased wife and is a subject of animal abuse.
- He is the catalyst for the entire John Wick series, as his killing of Daisy forced John back into action, which in turn resulted in the following action of the other movies.