If box office numbers are to be believed, it's safe to say most everyone has seen Avengers: Endgame and remembers when Tony Stark uses the Infinity Stones to defeat Thanos' army at the cost of his life. While that was an iconic and emotional moment in the MCU, Iron Man's acquisition and use of the legendary gems in the comics was a different kind of moment, where fallout from a superhero conspiracy threatened the world with the rise of a different kind of villain that forced Tony to wield the ultimate, life-threatening power mankind was never intended to behold.
In Avengers Vol.4 #7-12, writer Brian Michael Bendis and artist John Romita, Jr put the latest Avengers team to the test when they learn that somebody is out there collecting Infinity Stones (called Infinity Gems in the comics). Unbeknownst to the majority of Earth's superheroes, the Infinity Gems had been on the planet for some time, having been located by the Illuminati, a secret cabal consisting of prominent heroes who monitor and protect Earth from significant threats. After failing to destroy the Infinity Gems, the Illuminati decided to split them within its members, each hero tasked with hiding and keeping theirs safe. However, the knowledge of the deceased Black Bolt's hiding spot for his Infinity Gem became known to Parker Robbins, a criminal formerly known as the Hood. Seeking to restore his lost power, Robbins uses his money and connections to acquire two Infinity Gems, though his subsequent battle with the Red Hulk alerts the Avengers as well as the Illuminati to his plans.
Although the existence of the Illuminati was revealed to many of Earth's heroes as a result, few members felt the heat worse than Iron Man, who ended up in a losing argument with Steve Rogers. Rogers, who was acting as the current Director of SHIELD at the time, not only felt betrayed by Stark's secrecy, but declares that after the Avengers stop The Hood, Tony's time on the team was over. Despite their best efforts, the Avengers were unable to stop The Hood from acquiring all of the Infinity Gems, making him the first human being to do so. Unfortunately for Parker Robbins, who came so close to achieving his goal, he was not the first human being to do so as the Avengers managed to misdirect him with the reassembled Infinity Gauntlet wielded by Iron Man himself.
Ever the sore loser, Hood calls all the assembled heroes hypocrites who would have done the same thing if they lost their powers and challenges Iron Man, demanding what he would do. Faced with the infinite power of the gauntlet, Tony runs through the possibilities, both selfish and selfless, but ultimately decides on two things. First, he sends Parker Robbins back to his prison cell in the Raft, powerless and even more broken. Second, he uses the Infinity Gems' power to will themselves and the Gauntlet out of existence, correcting the Illuminati's mistake and eliminating the possibility of this event occurring again. These two acts of heroism seemingly redeemed Iron Man in everyone's eyes, including Steve Rogers, and saved his spot on the Avengers, proving that despite his flaws, Tony Stark was a real hero.
Unfortunately, Tony's act of heroism proves to be anything but. It was all an act and the Illuminati later meet to again split the Infinity Gems between their members. However this time, things have changed, as Steve Rogers is now a part of the Illuminati, agreeing with their cause and suggesting they need to hide the Gems in better places. Considering the threat both the Infinity Stones and the Illuminati would become to the Marvel universe, one could say that the MCU's Tony Stark was far more heroic than his comic book counterpart, but that wouldn't be fair. Both are simply different version of the same hero, doing their best to save and protect their world, even if their decisions don't speak well of their legacy.