The time-traveling warlord Kang the Conqueror knows how dangerous Iron Man is, so much so that he uses him as his ultimate weapon, even long after Tony Stark is actually dead. Iron Man's obsession with building powerful devices of destruction is a weakness that someone like Kang can easily exploit, even without Tony being aware of it.
Before becoming Iron Man, Tony Stark was a weapons merchant, who inherited this business from his father Howard. After being kidnapped and almost killed by terrorists, Tony invented the Iron Man armor and persona, and got out of the weapons business. However, he could not escape his obsessions, and he started building more and more advanced Iron Man armors and high-tech weapons. In theory, he does that as a security measure against possible threats to the world, but in reality, he is a deeply troubled man, with self-confidence issues and an inferiority complex. As a true futurist, Iron Man cannot help imagining the next advanced form of technology, however, more often than not it's in the form of weapons.
Related: Kang Secretly Exposes the One Weakness the Avengers Can Use to Beat Him
In Avengers vol. 4 #1, by Brian Michael Bendis, John Romita Jr., Klaus Janson, and Dean White, Kang the Conqueror exploits Iron Man's obsession in the worst possible way. Traveling to the past to warn the Avengers of a future crisis involving their children and Ultron, Kang is aware that the Earth's Mightiest Heroes will attack him on sight, considering their past encounters. To stop them, he threatens them with a device that Iron Man immediately recognizes: a dark matter accelerator that can instantly destroy New York and the Avengers. However, Tony is shocked because he never actually built that weapon, he
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