Darren Cross was the main antagonist of the Marvel Studios film Ant-Man. Former protégé of Dr. Hank Pym, he usurped control of his mentor's company and attempted to produce weapons based on Pym's work. He was portrayed by Corey Stoll.
Shortly after graduating from MIT at age twenty, Cross was employed by Hank Pym, CEO of Pym Technologies. During his time in Pym's employ, Cross frequently questioned his mentor about his revolutionary invention known as the Pym Particle. Pym insisted that the Pym Particle was an urban myth and that such research should not be pursued, but Cross was obsessed and began to view Pym as an obstacle that needed to be removed.
Over the years, Cross gained influence within Pym Technologies and convinced the board to vote Pym out of the company. He eventually restarted the research on the Pym Particle, attempting to develop a weaponized version of Pym's Ant-Man suit. By late 2015, Cross had successfully created the Yellowjacket, a suit equipped with Pym Particles that could allow the wearer to alter their size, augment their strength, and was equipped with flight capability and directed energy weaponry.
Cross later demonstrated the Yellowjacket suit to a group of potential buyers after inviting Dr. Pym to Cross Technologies so he could see Cross' success as well. However, he knew that the technology had not yet been perfected and he would need to conduct live tests with his Pym Particle variant before he could market it. Cross experimented with live lambs, but met with a long string of failures as his formula not only shrank the test subjects but turned them inside out. Eventually, Cross managed to perfect the formula and tested it without killing the subject.
Having at last perfected his Pym Particle variant, Cross hosted another presentation of the Yellowjacket suit at Cross Technologies. He had contacted members of the terrorist organization HYDRA and was planning on selling the suit to them. However, he had also learned that Hank Pym and his daughter Hope had enlisted the aid of ex-thief Scott Lang to try and steal his invention. Cross increased security all over his lab facility, expecting Scott to be using Pym's Ant-Man suit to break in. While Scott succeeded in entering the containment vessel holding the Yellowjacket, Cross was expecting him and sealed the container while Scott was still inside. Pym attempted to convince Cross not to sell the suit to HYDRA, but Cross refused to listen and threatened to kill Pym. However, Scott was able to break free; he and Hope began fighting Cross' guards, but Cross managed to shoot Pym.
As Scott and Hope ran to the bleeding Pym's aid, Cross stepped behind Lang and placed his gun to his head, threatening to kill him if he did not remove the Ant-Man suit immediately, to the point of even promising that he was willing to pull it off his corpse. However, before Cross could pull the trigger, he noticed that a group of ants had began crawling up his arm and biting into his skin, causing him incredible pain. Unable to fire the gun, Cross ran out the room while leaving Pym, Scott and Hope behind.
Cross ran to his guards while ripping ants off his skin. As he held one final ant between his fingers and slowly crushed it to death, the furious Cross demanded that a helicopter be brought to the roof immediately so he could escape. He then left two guards behind and ordered them to kill anyone who stepped out of the room without mercy before leaving to get on board the helicopter so he would not be arrested by the police that had gathered outside.
Ant-Man had chased after Cross' helicopter with a swarm of flying ants and boarded the chopper, shifting size constantly as he fought off Cross' guards. Cross continued to taunt Lang for attempting to stop all his plans with a heist, to which Lang clarified that he and Pym had never planned just a heist, which confused Cross and caused him to look on the Pym Technologies Headquarters. Cross watched in horror as Cross Technologies, along with his Yellowjacket research, was destroyed by the explosives Lang had planted throughout the building.
Enraged, Cross put on the Yellowjacket suit and fought Ant-Man on his own terms. In his fury, Cross began firing the lasers on his suit without any regard for his surroundings, critically damaging the chopper and killing the crew. With both pilots being killed accidentally by Yellowjacket's weapons, the helicopter span wildly out of control and both Cross and Lang tumbled into Cross' suitcase and fought a battle inside. As the furious Yellowjacket screamed and cursed at Ant-Man, his phone mistakenly heard his cries and played Disintegration by The Cure while they dodged the various keys and travel sweets that they each threw at one another as they continued to try to kill the other, all the while with Yellowjacket continuing to fire his lasers at Ant-Man, causing a lot of destruction within the small briefcase.
The briefcase fell from the out-of-control chopper, landing in a backyard swimming pool. The confused family members living on the property saw both Ant-Man and Yellowjacket appear from seemingly out of thin air, continually shifting in size as they fought. Ant-Man eventually returned to normal size and used a table tennis paddle to swat Cross into a nearby bug zapper, electrocuting him. However, this did not kill him.
Jim Paxton of the San Fransisco Police arrived at the house to arrest Lang, unaware that Cross was there as well. While Lang was being loaded into Paxton's car, Cross recovered from his electric shock and made his way to Paxton's house where Scott's ex-wife Maggie and his daughter Cassie were. While driving Scott to jail, Paxton received a call that someone had broken into his house. When they arrived, Scott and Paxton found Cross in Cassie's bedroom, holding the girl hostage.
Ant-Man and Yellowjacket fought once more, this time shrinking down and fighting on Cassie's toy railway tracks. Lang called for reinforcements from his army of ants who attacked Cross, before Lang was able to throw him into the train tracks, causing him to be run over by Cassie's little Thomas the Tank Engine toy.
Lang attempted to shrink and sabotage Cross's suit. However, he discovered the mainframe on the Yellowjacket suit was encased with a shell of titanium, which could not be penetrated unless the Ant-Man suit's regulator was deactivated; this would put Lang in danger of shrinking indefinitely. Frustrated by his inability to kill Lang during their fight, Cross then attempted to attack Cassie while she was being protected by Paxton. Although Paxton attempted to shoot Cross, he was quickly disarmed by one of the suit's arms, leaving him and Cassie defenseless against him.
As Cross prepared to murder the innocent family simply to torment his foe and gain a victory in this fight, Lang was left with no choice but to turn off his suit's regulator and sacrifice himself by shrinking into the Yellowjacket suit and damaging its internal mainframe. Cross screamed in horrific pain one last time before the suit then collapsed into itself, smashing the glass in his helmet and crushing his limbs until Cross' body was shrunk down enough to the point where he went subatomic. As such, Cross isn't so much dead as he is left in a constantly shrinking state, doomed to shrink into different quantum states forever.