Master Magician
Tony was a master magician, always doing a little wave, throwing a little sparkle and charm, and suddenly the audience was looking anywhere but where they should. It was the trick he had been perfecting since the first time he was kidnapped, at the ripe old age of five.
Razzle and dazzle worked. They made people think that they knew how the trick worked, that they knew what Tony was. They would pigeonhole him, assume that was all of it, and then were constantly surprised when there turned out to be more. When he pulled off one more daring, impossible, crazy plan.
Even Obadiah had been drawn in by the performance, forgetting what was underneath. His teammates, the Avengers, they tried. And sometimes they succeeded in seeing the truth, just a little. On their worst days, Bruce and Natasha, they recognized someone with a hole at the base of who they were, recognized that Tony was the same.
But, really, besides himself, there were three who really saw him. That were never fooled by the illusion because they believed the very worst, they knew the very worst, they were the very worst, so they saw it.
Fury had always had a back-up plan for Stark. And it was constantly being updated and changing and fixed. Because there was no one he had ever met who was more dangerous than Tony Stark.
Loki looked into those eyes, full of a darkness hidden so deep under all the tricks and treats, and the echo of himself was shocking. Disconcerting. And he decided that this man, as mortal as he appeared, would be the hardest to kill, because this man was wily, this man was preternaturally brilliant, this man was so much more than any of the rest of humanity. This man could be his destruction.
The last, the one who knew about that well of pain and rage and hate that bubbled up at the core of Tony, was also the one best able to affect the man. JARVIS knew Tony as thoroughly as he knew himself. JARVIS was raised with a knowledge of Tony both deep and true. There was no hiding from him, because he saw his creator for what the genius truly was - a step away from destroying reality.
The general public feared the Hulk, despised Black Widow and Hawkeye, were in awe of Captain America and Thor, and considered Tony to be the familiar and darling fool.
And of all of them, he would always be the most dangerous, partly because they discounted him so easily.
He would always be the most dangerous, because he had the most available. He had the greatest resources. He had the most powerful presence. And should something go wrong, should he lose those he cared for, should he reach that breaking point… Nothing could stand in his path to shatter the very world.
Tony Stark was a wizard, the most powerful of his age. And the most terrifying part was that he played at being nothing more than a simple stage magician. And while everyone watched the show, clapping and laughing and happy, no one saw the real magic reaching out to cradle or crack their lives.