HistoryHammer is Mr. Fix's mysterious employer who pays for the newly upgraded Whiplash 3.0 and hires him to capture himself (needing a solid alibi to throw off suspicion) and Obadiah Stane. While the latter was a success, when Iron Man tried to rescue Stane, Whiplash blew up his armor, assuming him dead.
Later on Hammer visits Tony Stark in the hospital and talks to him about him selling Stark International while Tony works on the tech. They would make billions, but Tony wouldn't sell, knowing he would just make weapons. During the conversation, they implied that they have met before. Later, when Iron Man comes back in his new suit, he succeeds in rescuing Obadiah this time. Mr. Fix got away into Hammer's limo where they meet in person for the first time. Hammer injects him with a nanovirus to blackmail him into building Hammer weapons that are so powerful that they will make Iron Man look obsolete.
Justin Hammer had Mr. Fix reassemble Living Laser in order to erase his memories and can use him to mass produce a weapon that he planned to sell to groups like A.I.M. or HYDRA and also to use him as research for "Project Titanium". But the Living Laser ends up splitting up into a Light Half and a Dark Half. After Living Laser was freed and reassembled, Justin Hammer scolds Mr. Fix for losing the Laser, but as a consolation prize, Justin Hammer was given the drive which contained the info they gathered for Project Titanium.
Justin Hammer was later seen buying the Iron Man armor specifications from the Ghost that he stole from Iron Man. He later uses the specs to create the Titanium Man armor and fights Iron Man with it when he breaks into his facility. He had the upper hand for a while but Iron Man and War Machine exploited the armor's weakness and won the battle. Blaming his failure on Mr. Fix, he activates the nanovirus inside him, killing his body. But he took out a chip holding his consciousness and implanted it into his computer so he can work on his projects 24/7, much to the dismay of Fix.
Hammer later schemed other plans like trying to steal an armor neural interface chip from Stark International and hiring the Black Widow to steal S.H.I.E.L.D.'s latest project, which is data and a sample of an adamantium/vibranium metal alloy, all of which were failures thanks to the efforts of Iron Man.
Justin Hammer is displeased that Obadiah Stane has landed the biggest military contract that surpassed Hammer Multinational. After firing a laser on the television, Justin Hammer orders Sasha to see if Mr. Fix 2.0 has finished the weapon which he plans use in order to put Hammer Multinational back on the top. Justin Hammer in his Titanium Man armor later ambushes Iron Man to call a ceasefire in a plot to take down Obadiah Stane and Iron Monger. When Iron Man refuses, Titanium Man attacks Iron Man. Sasha tells Justin that Obadiah Stane has snuck into Stark International. Upon using the Titanium Man armor to infiltrate Stark International, Justin Hammer manages to place a device that would place the Iron Monger armor under remote control. When Justin Hammer sees that Obadiah Stane has Pepper Potts, Sasha advises that Justin Hammer uses the Titanium Man armor to save Pepper Potts from Iron Monger which doesn't go well. After Whitney convinces her father not to kill Iron Man, Justin Hammer tells Sasha to take control of the Iron Monger armor and send it on a rampage. Iron Man discovers that someone is remote-controlling the Iron Monger and suspects that Titanium Man is behind this. When Justin asks for Sasha to help, Sasha controls the Iron Monger armor to target Whitney. Iron Monger then falls off the building as Titanium Man laughs at this. Iron Man and War Machine attack Titanium Man enough to blast him into the upper atmosphere with the Titanium Man armor disabled. He landed in a deserted mountain range, where his armor is powerless and he comically yells for help.
Hostile Takeover of Stark International
He eventually gets out of his powerless situation and announces to the public that he has bought Stark International. This eliminates Tony's right to inherit the company and his trust fund allowance (Tony uses this to build his armors and repair any damage to them), since it too came from Stark International. Hammer sets a trap for Iron Man at the docks where he gets beaten up by Whiplash, Killer Shrike, and Titanium Man, who were hired by Hammer along with Unicorn. They damage the armor and Tony passes out, but he engages lockdown mode on the armor. They take him back to Hammer's ocean fortress to remove the armor. They almost find out Iron Man's true face, until War Machine bursts in. Justin hits him with a cosmic energy barrier field, which slowly eliminates any organic material but leaves the armor intact. War Machine manages to free himself, while Pepper controlling the Stealth Armor reassembles and recharges the armor around Tony. Hammer runs away while the armored trio take out the rest of the villains. Hammer, in his Titanium Man suit, destroys the Stealth Armor and fights Iron Man and War Machine. They defeat him with the cosmic ray beam and make him pass out. Tony considers killing Titanium Man out of anger that he didn't get the evidence he needed, but Rhodey stops him and reassures that he will take back his company, by the book.
The Fall of Hammer
Justin Hammer has been receiving threatening messages from an unknown competitor. His increasing paranoia have drove him to develop a sinister zombie gas and use it to zombify Count Nefaria and to attack Unicorn and Killer Shrike senselessly as Titanium Man. Unicorn was badly hurt and Killer Shrike escapes, only to be taken down by Iron Man and taken to jail. Hammer later captures Killer Shrike from his prisoner transport and tortures him back at his lab. He insanely holds a gun to his head, but Iron Man and War Machine disarm him. Justin reveals his force-field wall and zombifies Killer Shrike. Iron Man later reveals his plan. The ravings that he said to Killer Shrike revealed his true colors as a criminal. They were being broadcast all over the world. Fix 2.0. did it as revenge for taking his body and turning him into a digital freak from Titanium vs Iron . Justin Hammer gets in his Titanium Man armor and unleashes a zombie gas bomb that is immune to Tony's Extremis on the city. Iron Man stops the gas with an incendiary bomb and stops Hammer's armor with Extremis. He throws him into his office, but Fix, not done with Hammer, takes his remote and locks him in the zombie gas chamber. He zombifies Justin Hammer. He is now remanded to SHIELD custody.