For those that have known about Tony Stark before the MCU was created this likely won’t come as much of a surprise since Stan Lee admitted, before his passing, that he created Tony Stark to be utterly unlikeable as a challenge to himself and to the fans. The character has obviously come far from the poisoned roots that Lee laid down at the beginning, but back in the day when he was first being brought to life, Stark was far more villain than hero. In the MCU his past has been revisited and kind of retconned to show him as a teen that didn’t get enough attention from his father, and then an adult that made several questionable and even wrong decisions since after the deaths of his parents he didn’t really have anyone to guide his genius and his temperament since Obadiah Stane was an enabler that wanted Tony’s genius and would only curb his other tendencies when they flew too far out of control. In other words, Tony was allowed to behave like a big, self-destructive kid so long as he continued to push his genius in a way that was profitable. Stan Lee actually had this to say about the character via ScreenRant:
“I think I gave myself a dare. It was the height of the Cold War. The readers, the young readers, if there was one thing they hated, it was war, it was the military. So I got a hero who represented that to the hundredth degree. He was a weapons manufacturer, he was providing weapons for the Army, he was rich, he was an industrialist. I thought it would be fun to take the kind of character that nobody would like, none of our readers would like, and shove him down their throats and make them like him … And he became very popular.”
The truth is that Tony Stark, in the comics, was a jerk beyond compare a lot of times. Even when he’d become a hero and wanted to do right, he was still egotistical and had to be the smartest person in the room since this was his personality. This part at least made it into the MCU since RDJ’s portrayal of a man that made horrible choices in the name of preserving humanity was spot-on. He had great motives, but they didn’t always work out the way he wanted since other factors were always working against him. Initially, it was Hank Pym that created Ultron, but since Pym belonged to Tony’s father’s generation in the MCU, and Scott Lang is smart but not super-smart like Tony, it fell to Stark to mess around and create an AI that would eventually turn on the Avengers. Plus, his idea to protect the earth in his own way was a bit unnerving but made sense from a certain point of view. In the comics, Tony was a complete jerk, an alcoholic, and was even kicked out of the Avengers at one point since he was considered too much of a liability. Trying to picture that now would be kind of funny since Stark was actually the source of the Avengers’ funding.
Plus, in the MCU, fans didn’t necessarily hate him so much as they pitied him since he obviously did have an issue with alcohol, even if it wasn’t touched upon in that big of a way. His ego was definitely a huge issue, but that was resolved fairly quickly, kind of, since in the first Iron Man movie he learned how to show at least some compassion for others after having been launched as a carefree and very irresponsible individual. As the movies progressed, so did his character, as from the first movie to Endgame there was a huge difference that was noticed as Tony not only started taking responsibility for his messes, but he started to promote and seek out the best in others as well, as he became Peter Parker’s mentor in a big way and also became a more integral part of the Avengers despite keeping his ego and bravado. But one thing that showed a lot of growth was his emotional response to Peter’s disappearance along with everyone else during the snap.
Some might say that he ran away after the events of Infinity War, but the truth is that he had to find a way to cope just as everyone else did. Much like many others, he had to watch someone fade away, not just die, but be erased from existence. That would definitely leave a scar that no one could possibly recover from, but for Tony, it was a mark of realizing that he did care about others and that his sense of right and wrong wasn’t so horribly skewed. But the most telling of all that he’d changed was his sacrifice, as despite coming into the Marvel universe as a heel and a truly unlikeable person, he went out as a true hero who was willing to give everything to preserve what he valued most.