Marked for Death

Chicago DEA agent John Hatcher (Seagal) has just returned from Colombia, where his partner Chico (Richard Delmonte) was killed in a confrontation with drug dealers, and John killed the dealers who killed Chico. As a result of Chico's death, John has decided to retire.One night, John and his friend Max (David), a local high school football team's head coach, go to a bar. A gun fight breaks out between local drug dealers and a Jamaican gang called the Jamaican Posse, whose leader is a drug kingpin known as Screwface (Basil Wallace). Hatcher arrests one of Screwface's henchmen as the gunfight ends.The next day, Screwface and some of his henchmen get revenge by shooting up the house that John, his sister Melissa (Gracen), and Melissa's 12-year-old daughter Tracey (Harris) live in. Tracey gets shot and is hospitalized in critical condition.Hatcher encounters a gangster named Jimmy Fingers (DiBenedetto) and unsuccessfully tries to get him to tell him where Screwface might be and is forced to kill him. Another Jamaican named Nesta (Evans) arrives and Hatcher is able to sit him down but Nesta tells him to go after Screwface alone and jumps out the window to his death. When asked what happened, John finds the blood symbol used by the Posse during the murders vandalized on a carpet the next day and gets information about it from a Jamaican voodoo and gang expert named Leslie (Pacula) who works part time as a detective.Hatcher comes out of retirement to join Max in a battle against Screwface. While John is in the detective's store, Melissa makes a phone call to him but is cut short when Screwface and his men invade into Hatcher's home and attempts to murder Melissa but they leave upon Hatcher's arrival.The next day, Hatcher and Max get into a fight with three of Screwface's henchmen during a car chase. The fight moves on to a mall after the henchmen's car crashes and the duo kill all three men there. At the house of Leslie, Hatcher now realizes that the only way to stop the Jamaican Posse is to bring down Screwface.The two team up with Charles (Wright), a Jamaican Chicago police officer who has been trailing Screwface for five years (since 1985). They gather all the weaponry they need from a local weapon dealer; machine guns, submachine guns, pistols, Suppressors (silencers), remote control bombs and head for Kingston, Jamaica to find Screwface. Upon their arrival, Max and Charles ask everyone in the streets for the location of Screwface's hideout. They meet a local Jamaican who presents them a photo of a woman who knows Screwface. Hatcher meets her in a club and she gives the address of Screwface's mansion. The woman also gives Seagal's character a cryptic clue about Screwface, stating that "The secret of ScrewFace' power is that him have (sic) two heads and four eyes."At night, Hatcher, Max and Charles (disguised as a Posse) head for Screwface's mansion where there is a party. They secretly infiltrate the premises through a plantation area nearby. Hatcher guns down three of the henchmen at the balcony and goes to a nearby power station and plants a bomb. He infiltrates the inner grounds by climbing on the roofs while Max and Charles monitor the activities. Hatcher detonates the bomb causing the party to erupt in mayhem and gunfire. Hatcher enters the building and disposes every henchmen. He finds a sacrificial area and is captured by Screwface and his remaining henchmen. Hatcher is able to break free and kills every henchmen before fighting Screwface. During the swordfight, he kicks dust to Screwface and puts the sword to Screwface's genitals and decapitates him.Back in Chicago, Hatcher displays Screwface's severed head to the Jamaican Posse to get them to leave town. However, Screwface's identical twin brother, who runs the Chicago Posse crime business arrives and kills Charles making the gang and the audience believe that Screwface returned from the dead where in fact he actually committed all the Screwface crimes in Chicago, such as trying to murder Hatcher and his sister. The meeting erupts into chaos and the gang open fire on the duo. While Max holds off the henchmen in the gunfight, Hatcher kills more gang members before dealing with Screwface's brother in a swordfight. The fight moves to the nightclub where Hatcher kills Screwface's brother by gouging his eyes and blinding him, breaking his back and dropping him down an elevator shaft, in which he gets impaled upon landing. The gang looks at their dead boss and with both the Screwface's dead are presumed to be arrested at the film's ending.The final scene shows Hatcher carrying Charles' body with Max limping next to him who was shot in the leg before the film ends with Jimmy Cliff's John Crow in the credits.

Question: What does John use to scare the Jamaican Posse away?
Answer: Severed head