Firepower was the result of some of Tony Stark’s worst behaviors and attitudes coming back to bite him all at once. He’d ticked off a rival businessman known as Edwin Cord, and his quest to recover his stolen technology during the legendary “Armor Wars” storyline lead to a U.S. military
project being repurposed specifically for the purpose of taking down Iron Man.
The suit was stronger and carried far more destructive weaponry than Iron Man expected, leading to Stark being absolutely decimated and his Silver Centurion suit being destroyed by Firepower’s surface-to-air missile. Fortunately Stark wasn’t in the suit when it happened, and his next model would have no trouble putting Firepower down.