Jack Hammer is a minor antagonist in the video game Phoenix Wright: Ace Attorney. Specifically, he is the posthumous main antagonist of the Turnabout Samurai chapter.
In 2011, Dee Vasquez witnessed a fight between Jack Hammer and a fellow actor named Manuel, who was also Vasquez's lover at the time. An accident occurred shortly after when Hammer accidentally pushed Manuel onto a sharp fencepost, which impaled and killed him. Due to Vasquez's mob contact, and also thanks to Wendy Oldbag keeping the picture for herself, the accident never leaked to the press. Vasquez then used the murder of Manuel to blackmail Hammer over the next five years.
Five years later, Jack planned to murder Vasquez. At first, it was thought to be solely for revenge over the blackmail, but it later turned out that he also hated the fact that Will Powers was more famous than he was. So he came up with a plan to frame Will (the person that looked up to him) for murder.
Jack first got Will to sprain his ankle during the rehearsal of a fight scene of their show, The Steel Samurai. Then, he drugged him with sleeping pills and took his costume. He then tried to kill Vasquez with the Steel Samurai spear, which ended up forcing Vasquez to push him to his death in self-defense. Ironically, he died the same way as he had unintentionally killed Manuel - by being impaled on the same fencepost that had impaled him five years prior.
Even though he was dead, he still manipulated everyone into framing Will, who almost had his life ruined. He also almost got Wendy Oldbag, who was a fan of his, arrested for murder. His actions also almost got defense attorney Phoenix Wright and his assistant, Maya Fey, killed. He also ruined Vasquez's career, as well as director Sal Manella's. In the end, everything he cared about was being famous and making money.
Little is specifically known of Hammer's personality, as he died before Wright could meet him unexpectedly. However, his actions seem to point out that Manuel's accidental act of causing death and the following extortion turned him into a bitter and argumentative man. He was deeply unlikable towards Vasquez, but also very resentful towards Powers. Hammer was forced to play a hated villain in a show in which Powers landed the lead heroic role.
To act in a way that makes a displeasing situation worse, he was then paid "peanuts" for his great deal of endurance. Upset with every hits to his widespread belief, he was driven to attempt murder. So Vasquez indirectly states that the death of Manuel was not an accident, but Hammer had intentionally done it. It is unconfirmed whether what she says that it is true, although she does want to know why else Hammer would let her mercilessly run his life otherwise.
Phoenix Wright: Ace Attorney: Spirit of Justice
Dai Gyakuten Saiban 2: Naruhodō Ryūnosuke no Kakugo