Here’s a 1987 Marvel Comics four-issue limited series of the Fantastic Four vs. the X-Men.
Issue #1
Reed Richards is called away from Four Freedoms Plaza, a request from Magneto, to help Wildcat – whose only hope is a device built by Reed Richards. Upon arriving at Muir Isle, Richards examines Wildcat and regretfully explains there’s nothing he can do. Wolverine isn’t too happy with that response, and unsurprisingly, starts a fight.
Issue #2
While the X-Men and Fantastic Four are fighting it out, a fisherman adrift on the open ocean is brought into safety. He appears to be an android/robot at first, but then transforms into a hologram of Dr. Doom. Doom says he can save Wildcat’s life, much to Reed Richard’s suspicion. But the X-Men are willing to take up his offer and ask Richards to leave.
Issue #3
After a lot of contemplation from the members of the Fantastic Four, who believe they have evidence that Reed Richards deliberately took them into a rocket to transform them into superheroes; and contemplation from the X-Men about whether to trust Magneto – the issue ends with the Fantastic Four reconciling and Dr Doom trying to save Wildcat.
Issue #4
The Fantastic Four return to Muir Isle, with Reed Richards believing he now has the means to save Shadowcat’s life. They don’t receive the most pleasant of receptions from the X-Men and once again a battle ensues. The short-lived fight is interrupted by Franklin Richards, the son of Reed and Sue Richards. Attention then shifts to the saving of Wildcat. Despite some heated arguments between Dr. Doom and Reed Richards, Wildcat recovers.