Warning: SPOILERS for Iron Man #25
Marvel's Iron Man is usually an ally of the X-Men, but he recently gained the power to exterminate the entire mutant nation of Krakoa - and Tony Stark refuses to let this power go. Before becoming a superhero and founding member of the Avengers, Stark was a weapons manufacturer and arms dealer, specializing in every weapon imaginable. In Iron Man #25, a cameo by one weapon in particular suggests Stark sees the X-Men as a threat, and has made plans to exterminate that threat if possible.
In current comics continuity, Iron Man has lost his entire fortune, though not without cause. The former billionaire encountered a mysterious company called Source Control, owner and dealer of exotic weaponry to multiple nations on Earth. Source Control's warehouses contain vast amounts of highly destructive materials, and instead of attacking them head-on, Stark decides to buy all their weapons outright. The final weapon Stark needs - the Ten Rings of the Mandarin - is unfortunately in the possession of Riri Williams aka Ironheart, who refuses to give the rings up. Stark has lost the rings, but he still has everything else.
In Iron Man #25, written by Christopher Cantwell with art by Angel Unzueta, Tony Stark has stashed all the Source Control weapons in a massive warehouse. Among those weapons is a giant severed head of a Sentinel: mutant-hunting machines that have existed in comics for decades. Perhaps their most famous usage, apart from multiple X-Men films, was in the Days of Future Past arc in which Sentinel patrolled the streets looking for any escaped mutants. This Sentinel is not intact - but Stark is highly skilled at reverse-engineering technology, and he could create a body easily if he wished.
Iron Man Holds The Key To Destroying The X-Men
Iron Man has hinted as his disdain for the X-Men before. In 2022's Hellfire Gala event, Stark talked to Emma Frost about the mutant capability of resurrection and mentioned that Krakoa's time was limited. Readers at the time couldn't imagine a scenario in which Stark would be the one to bring Krakoa down, but a few Stark-enhanced Sentinels would do just that. The X-Men are powerful, but their war with the Eternals suggests they are not invulnerable.
Iron Man, if he truly wanted to, could use an army of Sentinels to breach the Krakoa perimeter and destroy the society from within. The X-Men would undoubtedly retaliate with all their might and may even hurt Stark directly, but after creating such inventions as the Hulkbuster, Thorbuster and multiple other armors, Iron Man is adept at upscaling his technology to an absurd degree. The X-Men may even lose to Iron Man if he decided to attack, but for the moment, the two superhero communities are at peace - for now.