based on this gifset by tstarkismycopilot on Tumblr

Oh, man, the first time that Nick Fury had to deal with Tony Stark, the only description that he could find to fit the man was egomaniacal, petulant, spoiled, little shit.

You are not the center of my universe.

Nick should've left his sorry ass on that donut, and it would have made his life that much easier. But Nick had a side of himself that he hated, and that he hated for others to see; he was a compassionate man behind that tough veneer. It was a cloak that he wore because he had to, as the Director of SHIELD and as the protector of secrets that no one else wanted to guard. Often times, he could push that side of him away to get the job done, and in others, he could use that side to pull his team into jobs that they never wanted to do but still needed to be done. But when Tony was the focus of his attentions, either good or bad, there was something more going on; there was an uncomfortable sense of responsibility that he harbored for the kid, because yes, he saw Tony Stark as a lost kid for all intents. He saw a kid searching for direction and purpose, and Nick knew that he just happened to be the Director for the job.

We have a missile headed straight for the city.

Then Steve had all but dammed Tony to an uncertain fate with his challenge of Stark never being the one to make the sacrifice play, and Nick cringed at the words; he knew Tony well enough to know that if the moment came, he would make that play just to spite the Captain that he hated so much. When he alerted Tony of the nuclear missile heading into midtown New York, he didn't want to; his mind was screaming at him to shut up and to find another way, but there was none. Tony had to be the one to intercept it, as he was the only one who could.

"I know right where to put it," Tony said over the comms, cool and assured, but Nick knew that inside he was on the verge of panic. He could hear it in his voice. Maybe no one else did, and that was okay, because Tony would never want anyone else to know. As he watched Iron Man carry the weapon into the massive hole in the sky and into the black of space and a certain death, Nick felt a part of himself die with him, and he wasn't sure why. Tony wasn't his son, and wasn't even a friend, per se, but there was an undeniable sense of regret that he hadn't done better by him. He couldn't even bring himself to look at Maria when her own terror faced him, and he was ashamed of himself for the weakness.

You've come up with some pretty impressive inventions, Tony. War isn't one of them.

But after it was all stripped away, with SHIELD gone and Nick left as a man running to find his own purpose now, much as Tony was when he found him years before, he came to a new understanding of himself. Nick was a Director in title alone. Yes, he could run SHIELD with his one good eye closed and a hand tied behind his back, but what he couldn't do was be the leader that his team really needed. When the threat of extinction became a real possibility, and when Ultron was the one promising that end, Nick knew that Tony would be at new depths of self-blame for what he had done. He knew that it would cripple him, when his team and the world around him would need him the most. He knew that the time had come to be honest with the kid once and for all.

"I'm just an old man who cares very much about you," he said clearly, staring Tony down to be sure that he heard him; to be sure that he understood. It was a sensation that Tony didn't know very well, to feel open affection from someone like Nick, and as he looked away it was obvious that he didn't know what to say; he didn't know how to process this kind of love. It was a clear departure from the man that Tony was introduced to that day in that stupid donut, and as much as Nick wanted to curse and blame Howard for failing his own son, he had to come to the realization that it was what had brought the two to this moment.

Tony Stark still might not be the center of Nick Fury's universe, but he was pretty damned close.