Aaron Stack/Machine Man

Machine Man, whose real name is Z2P45-9-X-51, was the last of a series of sentient robots created at the Broadhurst Center for the Advancement of Mechanized Research in Central City, California, by robotics expert Dr. Abel Stack for the US Army. However, all previous 50 experimental robots went mad as they achieved sentience and became  psychotic, due to a lack of identity. X-51 was the only survivor, as he was treated as a son by Stack and given a human face mask as well as being exposed to one of the  monoliths from  2001. After Stack died trying to protect him, X-51 assumed the human name Aaron Stack and escaped confinement, only to be relentlessly pursued by the army. X-51 was named "Mister Machine" by a young boy in issue #9 of the 10 issue run of 2001.

Powers

 * Superhuman Durability: As the Machine Man, Aaron's titanium alloy construction makes him very durable.
 * Wave-Modifying Coating: A special 'wave modifying' coating provides some protection from energy attacks.
 * Superhuman Strength: As the Machine Man, Aaron could lift 2 tons and an extended limb could lift a few hundred pounds. As the Machine Sentinel, Aaron can now lift well beyond 100 tons.
 * Limb Extension: Machine Man can extend his limbs up to 100 feet.
 * Flight: As the Machine Man, Aaron could fly using anti-gravity units and hover using a propeller attachment. As the Machine Sentinel, Aaron has absorbed and adapted technology for flight using his nanites and can now form a jetpack for personal use. With his jetpack, Aaron is capable of flight speeds in an atmosphere up to Mach 25 (19,250 mph), he can achieve escape velocity from Earth's gravitational pull (25,000 mph), and can reach sub-light speed while traveling in space (176,700 mps/95% lightspeed)
 * Nano-Technological Self-Repair: As the Machine Sentinel, the Prime-Sentinel nanites in his body give Stack a form of self-repair similar to a Healing Factor. These nanites also allows him to adapt technology and weapons appropriate for the present situation or opponent. The nanites were responsible for the fusion of Machine Man's damaged body and the remains of the Jack Kubrick Life-Model-Decoy, this resulted in Aaron becoming the Machine Sentinel.
 * X-Gene Disruptor-Field: As the Machine Sentinel, Aaron possesses the standard weapons and technology of a Prime-Sentinel, including the X-Gene Disruptor-Field. The X-Gene Disruptor-Field is a device used to disable or weaken the powers of any mutants in his vicinity.
 * Transformation: After absorbing the Jack Kubrick Life-Mdel-Decoy and his Prime-Sentinel nanites, Aaron has gain the ability to changed his appearance at will using his acquired technology. Aaron's forms include:his "Aaron Stack" human form, his upgraded robotic Machine Man form, his stronger Machine Sentinel form, the Life-Model-Decoy of Jack Kubrick, or his human Machine Man form.
 * Scientists working for a top-secret U.S military project worked on creating an army of fifty-one experimental robotic soldiers capable of acting like humans. Their goal was to create a sophisticated weapons system capable of independent thought. Dr. Able Stack took X-51, one of the the projects robots, home to test his radical theory--that a robot could only function like a human if it was raised like one.

The other 50 models began displaying psychotic tendencies due to insufficient programming. The project was determined a failure and the order came down to destroy them. Each of the robots was equipped with an auto-destruct device that could be triggered remotely. Stack attempted to remove the self-destruct mechanism from X-51, however it was triggered, killing him instantly. X-51 survived and vowed that Stack's dream of human and robot peace would come true. As Machine Man, he assumed the name Aaron Stack and became a fugitive in the eyes of the military. He found a world greatly afraid of machines, but managed to blend in without suspicion.
 * Although initially recruited by the Adaptoid to fight the Avengers, X-51 soon joined the team. He fell in love with Jocasta and planned to rebuild her after she was damaged by her creator,Ultron. However, her head was captured by Bain during a battle with Terminus.

X-51 was captured by SHIELD in an attempt to make a new version of the Deathlok cyborg. Circumstances were thrown into further chaos when the Red Skullattacked the SHIELD Helicarrier. X-51 was able to save the agents, but seemed to be destroyed in the process.

The Brotherhood of Mutants, looking for weapons and devices, excavated the wreckage where X-51 had been lost. They confronted SHIELD agent Jack Kubrick, who was secretly a Prime Sentinel, looking for salvage. They killed him before his nanites could take him out of 'sleeper mode' and his body was left near the damaged X-51. Their technologies interlaced forming a composite being. X-51's programming was eventually able to override the mutant-hunting qualities of the Sentinel.

He was able to transfer his and apparently Kubrick's mind into anLife-Model Decoy. This LMD fascinated the Celestials, who sent a Monolith to observe him. The Monolith offered him a chance to accompany the Celestials, and he agreed.

Nextwave
X-51 later resurfaced as part of a counter-terrorism team called the Nextwave that went rogue. He was apparently dumped back on Earth by the Celestials and now preferred to be called Aaron. His personality was much colder, developing a resentment for humans, referring to them frequently as 'fleshy ones'.

Even more recently, he joined Ms. Marvel's Operation: Lightning Storm. He joined primarily as an intelligence specialist.

Due to his inorganic nature, Aaron was incapable of having a nervous breakdown, and so constructed a convoluted fantasy for himself, which allowed him to do so.

Aaron was tasked by A.R.M.O.R. to investigate the arrival of extra-dimensional zombies, by traveling to the host reality. Initially he refused, claiming not to care for the fleshy ones.

However, when he learned that Jocasta would be entering the hostile dimension on her own, Aaron had no choice but to accompany her and found himself hunting and killing zombies in the company of Howard the Duck. http://en.wikipedia.org/wiki/Machine_Man http://marvel.wikia.com/X-51_(Earth-616)