Marvel: Daredevil can see and its all thanks to Iron Man
Daredevil is one of Marvel's most iconic superheroes to have ever existed and continues to, in the pages of their comic books. The character is primarily known for his blindness, which he was inflicted with as a child following an accident involving radioactive chemical waste which destroyed his eyes after he tried to help an old man cross the road.
The superhero makes up for his blindness via his brilliant radar and other senses such as taste, sound, and smell, which he has attuned to sharp accuracy over the years.
He is also an exceptional combatant when he combines his martial arts training with his enhanced radar sense to fight his enemies. When not fighting crime, he serves as a district attorney seeking to fight the wrongdoings of criminals via the justice system.
Although Daredevil is blind and continues to be for most of his appearances in Marvel comics and shows, there was one story, set in an alternate reality, within the multiverse, where he regained his eyesight and for a while was able to see perfectly clearly, albeit on a temporary basis. It was all thanks to Iron Man or, to be more accurate, an alternate evil version of the Armored Avenger known as 'Superior Iron Man.'
Marvel: Iron Man cures Daredevil's blindness via a strain of Extremis
The story of Iron Man curing Daredevil's blindness takes place in the Marvel Comics storyline AXIS, which is set in an alternate reality where the morality of the superheroes and supervillains were reversed via a magic spell cast by Scarlet Witch and Doctor Doom. Those who were traditionally heroes such as the X-Men and Captain America turned to crime and those who were villains such as Magneto and Mystique became heroic individuals.
In this alternate reality, set within the Marvel multiverse, Tony Stark developed a new symbiotic suit of armor that could form around his skin, and then took a step back from active crimefighting. He then developed a phone application called Extremis 3.0, which he then gave to the public for free. The said application held the power to improve a person's attractiveness on a greater scale.
There was, however, a caveat to the application's usage; the user would become addicted to it like a drug and if he or she wanted to continue using it, would have to pay 100 dollars a day for renewal, which meant that the free trial version was only for a day.
If kept away from the application, the addicted user would become a zombie-like creature. Thus, Iron Man in essence profited off of people's suffering and if they wanted to use the app to feel good again, they would have to keep paying him.
Matt Murdock (Daredevil) soon caught wind of Iron Man's actions and attempted to shut down his operations. He set up a trap and lured Stark into it and initially had the upper hand only for Iron Man to overcome him and knock him out.
Daredevil then woke up to a big surprise: his eyesight had been restored thanks to Iron Man, who used a strain of the Extremis substance, which generates special abilities, to send a signal to Matt's ocular nerves and reduce the damage to his retinas, which allowed the otherwise blind Marvel hero to see.
However, Stark then mentioned that it was only temporary and that Murdock would need boosters, which he could only provide if he wanted to keep seeing his surroundings perfectly again. The former offered to give the boosters free of charge but Murdock then accused him of trying to buy the latter's approval and how Stark thought he was a divine figure. Iron Man was enraged by this insult.
Daredevil then attempted to stop Stark but ended up failing. He was then captured by the latter, who hooked him up to a machine and damaged his brain to such an extent that he lost his memory of his time as a crimefighter. Murdock then spent his time in the hospital with Stark telling him that he was taking care of all of the former's hospital bills.
Other Marvel heroes who turned to a life of crime or broke bad during the AXIS comic event were the X-Men who decided to rule over and oppress the human race, and Captain America, who decided to become a dictator and take over the world.