War Inc.

The film opens in a bar in Nunavut when hitman Brand Hauser (John Cusack) shoots and kills three men at the bar. He takes pictures of the men with his phone, sends the pictures, and then throws the phone into a burning garbage can.
Hauser is then seen on a plane getting directions and life advice from the on-board navigation system, Jerry (Montel Williams). He turns on his screen to receive a video call from the former Vice President (Dan Aykroyd) who gives him his next mission: to terminate Omar Sharif (Lyubomir Neikov), the CEO of the oil company Ugigas in Ugigistan. He tells Hauser that he will be working under the Viceroy, whose identity is still being withheld until further notice. He also tells Hauser that his cover will be a trade show host, working with Tamerlane, a huge corporation that specializes in advertising. He must produce a trade show and a gala wedding as a finale, and still manage to kill Omar Sharif before he makes his plane back to Ugigistan.
He is taken by a car to the safe Emerald City within the fictional war-torn desert country of Turaqistan. In the Tamerlane building, he meets Marsha (Joan Cusack), his assistant for the mission. Once inside the building, he notices a reporter, Natalie Hegalhuzen (Marisa Tomei) attempting unsuccessfully to get inside the Tamerlane building. Natalie attempts to find out why she can't get into Tamerlane, and after asking him several questions, is rushed out of the room by Hauser who doesn't want to reveal any personal details about himself. He does arrange for her to have drinks with him which she accepts. Hauser visits the Viceroy in a secret location hidden in a Popeye's restaurant, who tells him what he needs to do. The Viceroy (who cannot be seen, but only heard with an altered voice) informs Hauser that the grand finale of the Trade Show he's supposed to prepare will be a wedding for Yonica Babyyeah (Hilary Duff), an oversexed, Central Asian pop star. He meets briefly with her and her fiancÃ©, Ooq-Mi-Fay (Sergej TrifunoviÄ).
Later, Natalie meets Hauser at a restaurant where he gives her an all-access pass to the Trade Show. She arrives at the rehearsal and is greeted by Hauser and Marsha, who quickly go to watch Yonica's rehearsal. Her oversexed appearance and slight attraction for Hauser make him throw up on Natalie's coat and he walks out. After talking to Jerry in his car, he drinks some hot sauce and then has a flashback. He sees himself telling his fellow hitman Walken (Ben Kingsley) that he is tired of killing and wants to quit. He and Walken engage in a brief struggle in which he shoots Walken and leaves him for dead in the back of a garbage truck.
After receiving a delivery from a dry-cleaner in Germany, he goes to the hotel that Natalie stays in and gives her her coat, cleaned. He asks her out for coffee and confesses to her his habit of drinking hot sauce when he's nervous. She then confesses that she doesn't despise him at all, and the two build up a small friendship. He is later visited by Yonica in his office. She tries to seduce him, but he rebuffs her. He later sees her when he is in a restaurant with Sharif and Natalie. Hauser takes Natalie home, where she kisses him. Embarrassed, she quickly rushes out of the car. She sees him the next day and asks for a pass out of the Emerald City. He gives her a card that he received earlier by videomakers who are big in the Arts Community, and might give her a good lead. Hours later, he visits Yonica and listens to her sing a beautiful ballad; from here on out, he develops a paternal affection for her.
Meanwhile, Natalie buys the cover for a pornographic video that the videomakers were going to shoot on Yonica's wedding night, and leaks it to the American press. After a confrontation with Ooq-Mi-Fay (who was involved in the making of this video), Hauser decides that the only way to continue with the wedding peacefully is to blame everything on Ooq-Mi-Fay's friend Bhodi Bhundhang. Bhodi hunts him down and tries to kill him in a big house that Yonica is supposed to do an interview in. There, Hauser reveals his past to Natalie and Yonica, and how his wife was killed and his daughter was kidnapped. He is interrupted when he hears a gun and rushes to another room, where he is forced to fight Bhodi. He kills Bhodi in front of Natalie and Yonica, who flee the house, horrified. They rush off into a cab, where Yonica asks Natalie to be her bridesmaid; Natalie accepts. Six hours before the wedding, Hauser receives a ransom video from what appears to be a gang of terrorists, who have taken Natalie hostage. Hauser travels to a nearby city named Fallaf, saves Natalie, and makes it to Room 1101, where he had planned to meet and kill Sharif. Hauser has a change of heart and lets Sharif live, and in return is informed "the ultimate chicken-hawk is nearby". Realizing what this means Hauser goes to the Viceroy's secret location, and breaks down the glass to reveal the man behind the screen. The Viceroy is actually Walken â the man who killed Hauser's wife and kidnapped his daughter.
Hauser asks Walken what he did with his daughter, and finds out that Yonica was actually his daughter all along. He rushes to tell Yonica at the wedding, and arrives there right before Walken destroys the building, accidentally killing himself in the process. Fortunately, Hauser, Natalie, and Yonica survive, and rush off to a plane that Yonica and Ooq-Mi-Fay were supposed to fly off in. Once they are airborne, and have presumably escaped, we see a trailing missile about to strike the aircraft. The Vice President reveals his next plan to attack neighboring Ugigistan, blaming them for the bombing of the Emerald city, and terrorist incidents in Turaqistan.

Question: Who sings a beautiful ballad?
Answer: Yonica