Found the following article online, use it to answer the question: What is the full name of the character who seeks to obtain a seat at the High Table?

Four days after the events of the first film, former assassin John Wick retrieves his stolen 1969 Ford Mustang Mach 1 from a chop shop owned by Abram Tarasov, brother of Viggo and uncle of Iosef. John dispatches Tarasov's men in a violent rampage that heavily damages the Mustang, but spares Tarasov under the auspices of peace and returns home, cementing his weapons into the ground once again.
After car shop owner Aurelio takes John's Mustang for repairs, John is visited by Italian crime lord Santino D'Antonio. It is revealed that to complete his "impossible task"—which allowed him to retire and marry Helen—John asked Santino for help. As a form of contract, Santino swore John to a "marker", an unbreakable promise symbolized by a "blood oath" medallion. Santino presents the medallion to demand services from John, who declines, claiming that he is retired. In retaliation, Santino destroys John's home with a grenade launcher.
John travels to The Continental Hotel in New York City. Winston, the owner of the hotel, reminds John that if he rejects the marker, he will be violating one of the two unbreakable rules of the underworld: no blood on Continental grounds, and every marker must be honored. John reluctantly accepts his commitment and meets with Santino, who tasks him with assassinating his sister Gianna so he can claim her seat on the "High Table", a council of high-level crime lords. Santino sends Ares, his mute personal bodyguard, to surveil John.

Santino D'Antonio