Fantastic Four (1961) 121-A

"The Mysterious Mind-Blowing Secret of Gabriel!"

The Fantastic Four battle Gabriel but they have no hope of defeating him and Gabriel proclaims that he will spare the Earth if humanity kills the FF.

Now the FF are on the run from all of humanity and Gabriel. That does not stop the FF from trying to destroy Gabriel but it is another who comes to the rescue, the only being with cosmic powers to save Earth, the Silver Surfer.

The Surfer defeats Gabriel and exposes him as a sham, Gabriel is a robot who was sent to Earth to destroy the FF and the Silver Surfer by Gabriel's creator, Galactus.