Read more about The Guardsman at: Wikipedia

Official Site: Marvel Comics

Guardsman was the name of a superhero in the Marvel Universe, but was later applied to a small squad of agents. He/they wear suits of power armor while working security at the Vault; the suits were designed by Tony Stark, better known as the superhero Iron Man.

The first Guardsman was Kevin O'Brien, who was born in Chicago, Illinois. He was an engineer and inventor working for the newly-opened Lakani Island plant of Stark Industries who came to the attention of Tony Stark when he invented a stun-ray that managed to harmlessly disperse a crowd of violent protestors. Stark invited O'Brien to transfer to Stark's main plant on Long Island, New York, and he accepted. Despite a careless streak that once caused the laboratory he was working in to explode, he became a close friend of Stark, and was soon appointed head of Stark's research department. On several occasions, O'Brien assisted Stark and his supposed bodyguard Iron Man (really Stark himself), notably against the Spymaster and his assistants the Espionage Elite, saving Stark's life on more than one occasion. Stark then decided to reveal to O'Brien that he was secretly Iron Man, and to build for him a second suit of armor for use in the event of an emergency. That emergency would come a short time later, when Iron Man and his girlfriend Marianne Rogers were taken captive by the superhuman madman Mikas the Soulfather. Putting on the armor before it was fully tested, O'Brien fell prey to a malfunction in the cybernetic circuitry controlling the armor which apparently stimulated the regions of the brain where rage and jealousy originate.

O'Brien found himself seized with sudden attraction for Stark's girlfriend Marianne Rogers, and became extremely jealous of Stark's power, looks and fortune. At the same time, Simon Gilbert, then Chairman of the Board of Stark Industries' stockholders, grew alarmed that Stark was moving out of munitions production and mapped strategies with the board to seize controlling interest in the firm from its principal stockholder, Stark himself. O'Brien—clad in armor and calling himself the Guardsman—offered to aid the board in their plot against Stark. As a show of support, he agreed to quell a protest rally outside the plant. The Guardsman aimed his repulsor rays at the crowd, injuring four protestors. Sickened by what he did, O'Brien turned on the renegade board members, roughing them up. But seeing Tony Stark with Marianne Rogers caused him to once again become unbalanced and he went outside to vent his rage on the growing crowd of protestors. Stark donned his Iron Man armor and engaged the Guardsman in battle to prevent him from doing more damage. Losing, the Guardsman sought refuge in an experimental tank. In an attempt to stop him without hurting him, Iron Man trained his repulsor rays on the vehicle and accidentally hit its fuel supply. The tank exploded, killing O'Brien.

Michael O'Brien was born in Chicago, Illinois. Some months after his brother Kevin's death, when the details of the incident came to public light, Michael, a sergeant on the New York City police force, decided that the official investigation exonerating Iron Man's actions was a cover-up. Reopening the investigation without official sanction, detective O'Brien confronted Stark, interrogated several of his employees, and declared his intention of proving Stark responsible for his brother's death.

The Guardsman has not been a contender in any CBUB matches.