Warning! Spoilers for Iron Man #1 (2020) below!
As part of the Avengers, Iron Man has faced some of Marvel Comics' most powerful villains: Thanos, Ultron, Kang, and more. But Iron Man's solo villains tend to be on his level: Whiplash, Crimson Dynamo, and other men and women in suits. Like his counterpart Captain America, Iron Man is happy to punch above his weight class, as long as he has godlike friends to back him up. In the new Iron Man series, Tony Stark is all by himself against a rarely-seen cosmic villain so dangerous that the Avengers and Guardians of the Galaxy once teamed up to stand against him... and he defeated them all.
Iron Man #1 is written by Christopher Cantwell with art by Cafu and lettering by Joe Caramagna. The series acts as a fresh slate after the previous run by writer Dan Slott and a variety of artists, including Christos Gage and Valerio Schiti. At the outset, Tony Stark sells all his tech at a steep loss to move back to New York and buy a brownstone and a beater sedan. He throws a party for people he hates, tries to garner some sympathy from his friend Patsy Walker, and when neither improves his mood, he fights one of his classic foes, Unicorn.
Unicorn is also going through some stuff, having found a purpose in worshipping "The Other", a being he refers to as "our monotheistic god". Tony takes Unicorn down, but in apparent retribution is struck by a bolt of lightning. The issue's final page is a lingering shot of a scientist Tony snubbed at the aforementioned party who had approached him with a pitch for a device that captures lightning as usable energy. The scientist's face is obscured by a field of stars, foreshadowing that he is more than he seems.
Thanks to solicitations for future issues of Iron Man, we know that's true. The next issue's preview tells us that "lurking on the horizon is a threat Tony—and indeed the entire cosmos—hasn’t seen in years…KORVAC". The name won't mean much to most fans, but Korvac is one of the heaviest hitters in Marvel Comics.
Back in 1978, the Avengers were visited by the Guardians of the Galaxy - the original version who lived in the 31st century—who had time-traveled to the past to capture a fugitive cyborg named Korvac. But unbeknownst to them, Korvac had happened on Galactus and stolen the Power Cosmic, which he used to transform himself into a god, then blend in on Earth as a human named Michael. But Michael was such a tremendous danger that the Collector tried to kidnap and preserve them, sensing that they would soon be annihilated.
Together, the Guardians and the largest Avengers team up to that point confront him, learning that he plans to use his omnipotence to remake the universe. They rush him and he kills them easily. The last one standing is Thor; when Korvac's cosmic-powered girlfriend tries to defend him, Thor kills her, and watching her die makes Korvac remorseful. In the end, Korvac loses interest and leaves. He restores the defeated heroes to life and vanishes.
Why is Iron Man facing a hero that he couldn't beat with a superhero army? According to a Marvel.com interview, series writer Cantwell sees Tony as being driven by a god complex and thinks his perfect foil is an actual god in human form. Maybe Iron Man doesn't have to overpower Korvac, just learn a lesson. Better that than dying again.