The Matador

An encounter in the bar of the Mexico City branch of the Camino Real Hotels, between tired businessman Danny Wright (Greg Kinnear), hoping to land a life-saving contract in Mexico, and jaded, falling-apart-at-the-seams assassin Julian Noble (Pierce Brosnan), leads both men into an awkward friendship. Julian is confronting the immorality of his profession and experiencing a mid-life crisis that causes him to freeze on a job; Danny is fearing that a vitally important deal will fall through and cost him his job. After an uncomfortable-at-times conversation, Danny leaves the bar. Julian apologizes and invites him to see a bullfight. During the spectacle, Julian reveals the kind of work he truly does, and when Danny is skeptical, takes Danny through the steps of murdering a portly spectator in the arena bathroom. Danny is shocked at how easily Julian can get within inches of the man, even though Julian ends the "tutorial" without going through with the murder.
Later, while at an outdoor cafe, Julian asks Danny to assist him in "facilitating a fatality"; Danny flatly refuses and Julian leaves. On leaving the idea seems to be that Julian has had enough of Danny and their friendship has just ended. That evening Julian appears at Danny's hotel room, knocking on the door, pleading to be let in; Julian wants to apologize for attempting to involve Danny in his work. Danny sits within looking undecided, and the scene fades to black without revealing what happened next. There is the sound of glass breaking once the screen goes dark.
The film picks up again six months later, during the Christmas season. Danny and his wife, Bean (Hope Davis) are relaxing at their home when Julian arrives, looking for a place to stay. Danny and Bean have reservations about the situation, but decide to let him in. The grateful Julian notices that Danny has framed the ticket from the bullfight, an act that affects Julian profoundly. That night, he shares the real reason for his visit: he needs help with one last job. Julian convinces Danny to go along with the plan because, he tells Danny, "you owe me." After much internal struggle and with Danny talking him through it, Julian completes the task at a Tucson horse race track.
On the plane back from Tucson, Julian reveals that the man he just killed was his boss. Killing the boss means now Julian can retire and spend the rest of his life in Greece. Danny is surprised, then amused at Julian's craftiness, but is reminded of Julian's lethal personality when he lightly punches Julian in the shoulder and is sternly warned by Julian, "Don't ever hit me again." Danny remembers his friend is still a killer and immediately apologizes. A split flashback sequence during the flight home (memories triggered by a statement Danny makes), shows what took place a year prior when Danny let Julian into his hotel room: Julian talked Danny out of commissioning a hit on a rival to win the Mexico City business deal.
Later, Danny and Bean are shown at the grave of their son, something they do together every year. Julian watches respectfully from a distance, places plane tickets for Greece (his intended place of retirement) on their car windshield, then slips away.

Question: Who did Julian kill?
Answer: His boss.