Jack Frontier was a former Hollywood action star turned terrorist who worked with Piet Gruber. He was previously an Army soldier and a CIA operative. He was the second main antagonist of Die Hard: Vendetta.
He is considered non-canon with the Die Hard series overall.
Die Hard: Vendetta[]
Gunmen working for Frontier stormed the Chinese theater in order to retrieve stolen works of art when John McClane arrived and took a number of them out. Frontier and his men then fled through the sewer system. McClane pursued but the villains escaped.
McClane then learned that Frontier was in fact working with Piet Gruber, the son and nephew of his old foes Hans and Simon Gruber respectively. Frontier's men then arrived at the Century City LAPD station and in the commotion, Gruber kidnapped Lucy McClane, John's daughter.
At the Fernandez Warehouse, Frontier taunts McClane that the city has decided to pay him and Gruber the ransom money and Lucy is still the bargaining chip, before leaving Marlin to fight the cop.
McClane pursued Gruber to the Nakatomi Plaza, where he had killed his father Hans. He faced down Gruber and Frontier on the roof, when Frontier suddenly jumped into the escape helicopter and abandoned Gruber, leaving him to be shot to death by John and Lucy. McClane then pursued by leaping onto the helicopter as it made it's way towards the Holmes Observatory.
Frontier revealed that his true plan was to lay siege to the premiere of a sequel to one of his own pictures, which was taking place at the observatory. McClane made his way inside as multiple bombs began to detonate around him, eliminating any of Frontier's men which stood in his way. In their final confrontation, Frontier mocked McClane before being shot by him. McClane then fled as the evacuated building exploded with Frontier still inside.