Successfully complete the indicated task to unlock the corresponding armor. Story mode missions unlock One Man Army missions. One Man Army missions will unlock specific armor for the One Man Army missions and completed missions in Mission Archive mode.
Classic: Successfully complete the "One Man Army vs. Mercs" challenge, which is unlocked after Story mode mission 7 (Arctic Battle).
Classic Mark I: Successfully complete the "One Man Army vs. AIM" challenge, which is unlocked after Story mode mission 8 (Lost Destroyer).
Extremis: Successfully complete the "One Man Army vs. Maggia" challenge, which is unlocked after Story mode mission 4 (Maggia Factories). Extremis is capable of stealth. It has a shockwave attack in place of grenades and missiles. It is very efficient and powerful.
Hulkbuster: Successfully complete the "One Man Army vs. AIM-X" challenge, which is unlocked after Story mode mission AIM-X, where you must destroy four power couplings before any are repaired, then defeat Horgan and his giant cannon. Hulkbuster is slow but can sustain massive amounts of damage. Its Repulsors are more like cannon shots, and in place of grenades and missiles is a single cannon shot that hits a target, then a moment later creates an explosive shockwave. It is perfect for groups of enemies.
Mark II: Successfully complete the "One Man Army vs. Ten Rings" challenge, which is unlocked after Story mode mission 3 (Stark Weapons).
Ultimate: Successfully complete the game. The Ultimate armor is the equivalent of the Extremis but does not have stealth, has a more powerful Unibeam, and Gatling Repulsors that are weaker but acceptable.
This is a very challenging mission, with anti-air defenses everywhere. Immediately go for the couplings. Take as little time as possible on defensive units. If you take your time destroying them and go on to other couplings, the couplings will be repaired and defenses will be reinforced. Immediately after their destruction, go to the center and destroy defenses. Hide under the platform to recharge your armor. Once the defenses are substantially diminished, go to the top and strafe Horgan, keeping the cannon below and in front of you. When he charges his attack, drop behind the cannon. He will hit it and damage it. After a few times of doing this, not only will you defeat Horgan but also get the hero objective of destroying the cannon.
Go to the fortress' jamming device. Next to it is a door mounted to the bottom of the fortress. Fly up inside, and destroy the four boxes that will take down the shields of the cannons. Fly back down. Go around, and fly to the highest point. Take out the cannons with your missiles. Jarvis will tell you to go inside. Tap into the computer, and come back out. Destroy the four engines, then destroy the top of the craft. Go back inside to another door. Open the big loading bay door, and fly inside. There may be a few mines dropped on the city below. Destroy the mine, and go back into the loading bay doors. Destroy the big blue cannon to go inside. Straddle between the two orange power engines to complete the level.
In One Man Army missions, destroy as many air units as possible quickly, especially jets as they are too fast to chase and difficult to shoot down. This is especially true in Arctic Battle and the One Man Army Mission 3 (vs. Mercs), as the jets are difficult and required to complete the mission. Take them out as they fly off the runway to defeat them effectively.
After the game loads, select "Credits" at the main menu. You will now be able to hear the full "Iron Man" song.