Cosmic Civil War
After the Collector used most of the ISO-Sphere's energy to defeat Maestro, Iron Man decided to take the opportunity to defeat him, seize control over the ISO-Sphere, and end the Contest of Champions once and for all.
To accomplish this mission, Iron Man sought out the other Champions of Battlerealm to help him, but not all of them agreed with him. Those who agreed with him joined his Iron Faction, while those who didn't joined Captain America's Blue Faction, and what was a disagreement between Iron Man and Captain America quickly escalated into an open conflict between the two forces.
Iron Man was also joined by his fellow Illuminati, who helped him to take the Blue Faction down through special missions. In one of said missions, the Illuminati were ordered by Iron Man to take a Captain America who had just entered the contest down, to their dismay.
As time passed, Iron Man became colder and more ruthless, hunting down his enemies without mercy. That led many of his allies to leave his side in order to help Doctor Strange find the legendary Civil Warrior to convince him to end the war.
Iron Man, along with Captain America, were defeated by the Civil Warrior in the site of their final battle, thus ending the Cosmic Civil War. He was among the champions who were recaptured by the Collector by the end of the war.