Lawless

During the Prohibition era, the Bondurant brothers -- Forrest (Tom Hardy), Howard (Jason Clarke) and Jack (Shia LaBeouf) -- run a successful liquor bootlegging business in Franklin County, Virginia, with the help of their friend, Cricket Pate (Dane DeHaan), using their bar as a front for their illegal activities.One day, Jack witnesses mobster Floyd Banner (Gary Oldman) eliminating a competitor and they exchange looks before Jack returns to the bar, where Forrest hires Maggie Beauford (Jessica Chastain), a dancer from Chicago, to be their new waitress. Shortly afterwards, the bar is visited by brutal Special Agent Charlie Rakes (Guy Pearce), on behalf of District Attorney Mason Wardell. Rakes informs Forrest that he wants a cut of all profit made by Franklin's bootleggers, but Forrest refuses and threatens to kill Rakes if he returns. Forrest later meets with the other bootleggers and convinces them to stand up to Rakes as well, though they eventually give in to Rakes' violent intimidation tactics.Meanwhile, Jack meets Bertha Minnix (Mia Wasikowska), daughter of the local preacher. He attends the church drunk and makes a fool of himself, causing Bertha's father to forbid her from seeing him, which only makes her more interested in Jack, with whom she flirts. Jack later finds Rakes raiding Cricket's house in search of his distilation equipment. When they don't find it, Rakes brutally beats Jack when he tries to intervene. Forrest hears of this and tells Jack that he needs to learn how to fight for himself.Forrest and Howard arrange to meet with potential clients from Chicago, but Howard misses his appointment to get drunk with a friend, and Forrest ends up beating the two men with Cricket's help when they harrass Maggie. Later, after Cricket leaves, the men return, slash Forrest's throat, and rape Maggie.Howard and Jack meet a surviving Forrest at the hospital, and Jack decides to travel to Chicago with Cricket to sell the liquor. Arriving there, they are doublecrossed by their clients, but are rescued by Banner, who recognizes Jack. Banner already knows of the attack on Forrest, as well as the identities of the two assailants, and he provides Jack with their address, and also advises Jack that they are working for Rakes. Forrest and Howard later find, torture, and kill the men to send a message to Rakes.Banner becomes a regular client of the brothers, who move their distilation equipment to the woods and have great profit. The money allows Jack to continue courting Bertha, while Forrest begins a relationship with Maggie after she moves into the bar for her safety, though she doesn't tell him she was raped.Jack eventually decides to show Bertha the distilation center, but they are ambushed by Rakes and his men, who had followed her. Howard incapacitates Rakes and Jack nearly kills him before they are forced to flee from Rakes's men with Bertha and Cricket, who is later recaptured and murdered by Rakes, who snaps his neck.
Wanting revenge for Cricket's death, Jack goes to confront Rakes and his men at a roadblock in the local bridge. Howard follows after him, rallying the bootleggers to come to their aid. Forrest decides to join them, though Maggie tries to dissuade him, telling him that it was she who had found him with his throat slashed and took him to the hospital. Forrest realizes then that she was also attacked that night, but Maggie continues to deny having been raped.The bootleggers engage Rakes' men in a violent firefight, during which Rakes shoots Forrest multiple times before being shot in the leg and attempting to escape. A wounded Jack follows him to the bridge and shoots Rakes in the chest, wounding him. Howard later stabs Rakes with a large knife and leaves him to bleed to death.
With Rakes and his men dead, the Bondurant Brothers decide to save their money and retire after Prohibition ends. Jack marries Bertha, Forrest marries Maggie, and Howard marries a local woman, all having children.
During a reunion at Jack's house, Forrest drunkly dances on a frozen lake and falls into the freezing water, dying of pneumonia a few weeks later.from wikipedia.org

Question: What does Forrest threaten if Rakes returns to the bar?
Answer: To kill him.