The Badoon take over Arkon’s dimension, someone escapes to get help, and the Badoon capture the Fantastic Four (who tried to protect the escapee).
The X-Men go save the FF, with Arkon.
That’s about it.
It’s an annual, so it’s a simple, big-fight tale. Perfectly fine for what it is, but nothing great. Except that tag line: Ou, La, La, Badoon! My younger readers probably won’t get the reference, but it is the catch phrase from a ubiquitous TV commercial for an old brand of jeans.