If there’s one thing comic books are known for, it’s crossover events. Some of them are good, some of them are among Marvel's worst yet either way they remain a staple of the superhero genre. No decade was more over-saturated with bad crossover events than the '90s, and one of the most infamous events of that decade dealt with the invincible Iron Man being killed and replaced by his teenage self after turning evil. Welcome to The Crossing, an Avengers comic featuring time travel, brainwashing, and one veteran superhero being transformed into a bug woman.
The Crossing first began publication in 1995, spanning six main issues in The Avengers written by Bob Harras (now editor-in-chief at DC comics) with art by Mike Deodato jr. and Terry Kavanagh. This doesn't include the multiple tie-in issues of Iron Man, Force Works, and War Machine that are almost mandatory to understand what's going on. The plot of the comic is centered around Kang the conquerer, a time traveler from the future and one of the oldest Avengers villains and his quest to destroy the Avengers while plotting to do... something.
Most Kang stories tend to be confusing, because technically Kang is three different supervillains who are all supposed to be the same person from different periods of time that all independently have fought the Avengers. The prologue to the comic stars Yellowjacket- no, not that Yellowjacket- Rita Demara, a time travelling hero and successor to the Yellowjacket name who has just returned from an apocalyptic future where the Avengers are all dead. After trying to warn the heroes of the Present, she's killed by Iron Man for... unknown reasons. The comic then features two more rapid-fire character deaths to up the stakes, setting up The Crossing like a murder mystery. An Avenger (revealed to be Stark at the end of the issue) has killed two people, and the audience has no idea why.
It isn't explained very well in the main story, but reading Force Works explains that Iron Man has apparently been the brainwashed thrall of Kang ever since they first fought each other -- making Stark a double agent for over 30 years, which is a serious retcon to give one of the founding Avengers. What exactly Iron Man was doing as a spy isn't made clear, but Kang needed him for something, and is now calling him back to the future to assist in his plans for world domination. Eventually the other Avengers find out something is up with Tony Stark, and band together to stop him... only for Tony to escape with the help of Kang's time-traveling minions. During his escape Janet Van Dyne, the original Wasp gets critically injured by Tony. Hank Pym swears that he will save her life right before Janet... transforms into a cocoon? Remember this for later.
With the Avengers mansion destroyed, the heroes are fortunately contacted by another time traveler named Luna, a member of Kang's inner circle in the future who has decided to betray them. She's being pursued by more of Kang's baddies and during the fighting is killed. The Luna of the Future dies in the same issue, but manages to tell the Avengers about an apparent time portal that exists in the basement of the Avengers mansion. During the ensuing battles, the Avengers are also rejoined by the Wasp (now a bright Pink Human-insect hybrid) and the Avengers fight off a group of Kang's minions. After the battle, Masque (yet another traveler from the future) rationalizes that the only way to stop an evil Iron Man is to find a good Iron Man to fight him, so the Avengers decide to go back in time... to recruit a 19 year old Tony Stark to fight the Iron Man of the present, turning this already confusing story into a confusing Time Travel story.
Finally, the most confusing part of the event. Time travel is hard to pull off in fiction and comic book time travel is probably even more complicated. After arriving in the past, the Avengers do battle with more minions of Kang, and manage to recruit the teenage Tony, and bring him to the present. This new Iron Man manages to acquire his own Iron Man suit just in time to save the Avengers from Kang's robot army. Teen Tony does battle with his future self but is defeated, leaving the Avengers to fight a newly arrived Kang and Mantis without him. During the final battle, Adult Tony finally breaks free from Kang's brainwashing, defeats Kang's army and sacrifices his life to stop him, mercifully ending this event.
The Crossing was supposed to be Iron Man's swan song as he was permanently replaced by the time-traveling teen Tony. Fortunately Teen Iron Man barely lasted a year before dying in Onslaught, another bloated '90s crossover comic. The original Iron Man was brought back to life by Franklin Richards in Heroes Reborn, Kurt Busiek's attempt to sort out the continuity issues in the Marvel universe. Part of Busiek's retcons took place in Avengers Forever which had to explain that the reason Mantis and Swordsman were so out of character is because they were clones created by Immortus, another one of Kang's identities. This helps fix the issue with Mantis' character, but it also makes The Crossing even more confusing in hindsight.
As for Tony's crimes, an Avengers tribunal led by Captain America eventually absolves him of his crimes, reasoning that Kang was actually responsible. Depending on who you ask, these murders aren't even the worst things Iron Man's ever done, but at least this time he isn't the one responsible. The Crossing tried to redefine Tony Stark as a character, but instead it ended up one of the most confusing and embarrassing adventures Iron Man has ever starred in.