Hitman

In Hong Kong, a hitman known as the "King of Killers" has murdered a wealthy ex-yakuza crime boss named Tsukamoto. Because Tsukamoto had established a revenge fund in case of an assassination, a $100 million bounty is placed upon the King of Killers. The deceased's power hungry grandson, Eiji, becomes the new head of the Tsukamoto family and one of the bounty hunters.
An ex-soldier named Fu is part of a small gang that learns of the bounty. Fu attempts to enter the building where Tsukamoto's lawyers are discussing the terms of the revenge fund, but is rebuffed by the security. When he defends himself, his martial arts skills attract the attention of Lo, a seedy small-time criminal. Lo is also seeking the bounty on the King of Killers, and agrees to hire Fu as his muscle. They are warned not to pursue the case further by Inspector Chan, a member of the Hong Kong Security Bureau. To test Fu's abilities, Lo takes on a small contract to kill a local gang member, while also outfitting Fu and allowing the ex-soldier to live in his home. Fu soon meets Kiki, Lo's daughter, who is a successful attorney and ashamed of her father's sleazy activities.
Martin, the head lawyer in charge of Tsukamoto's revenge fund, makes the discovery that prior to his death, the crime lord was forced to swallow old Chinese wartime promissory notes. He sells this information to the bounty hunters, and as Eiji is willing to pay the highest amount, he is the first to learn the serial codes on the notes. Fu and Lo follow Eiji to a small apartment complex, where they learn that the suspect is an old man named Uncle Leung, an acquaintance of Lo's that he had previously been searching for. Despite their best efforts, Fu and Lo are unable to extract Leung, who suffers a heart attack and dies during their escape and is then shot in the head by Eiji.
Back at Lo's apartment, Lo comes clean with Fu: Years ago, he had met Uncle Leung, and in talking with him learned the old man was a veteran whose entire family was killed by the Japanese during the Second Sino-Japanese War. Now Leung wanted vengeance on his family's murderers, but the only wealth he possessed were the promissory notes. Taking pity on an old man, Lo told Leung to hold onto the notes and, in the event of the murder of the Japanese man he wanted dead, cash them in and forward the money to his bank account. Lo had only recently learned that Tsukamoto was the man Leung wanted to have killed, and once the crime lord had been assassinated by the King of Killers, Leung had done what Lo asked and forwarded the money from the notes to Lo's bank account. This had created a paper trail that implicated Lo as the King of Killers.
Before Fu and Lo can plan further, their apartment is suddenly attacked by the bounty hunters. They are able to barely escape, and Lo makes plans to disappear to mainland China. Before they leave however, they decide to attend Kiki's wedding. At the event, Fu once again meets Inspector Chan and deduces that the agent is actually the real King of Killers when he slips that he knows Lo is not really the wanted assassin. Fu and Lo then go to Eiji's penthouse to meet Martin, where Fu shoots Lo and demands to cash in on the bounty. Martin however informs them that Eiji has changed the terms of the fund so that no matter who kills the King of Killers, he will be the one who receives the money.
A massive fight ensues in the penthouse and soon Inspector Chan arrives as the King of Killers to help Fu and Lo. They are able to kill Eiji and all of his men, leaving Martin to rewrite the terms of the fund. Later, they are seen together, dividing up the money and discussing their future plans. Chan retires, and recruits Fu to act as the new King of Killers.

Question: Who is Lo seeking the bounty on?
Answer: King of Killers