"The Hate Monger" (X-488) by Lee and Kirby/Bell; 22 pages.
A new menace arises, as the mysterious Hate Monger sows hatred through the world via his H-Ray gun. The FF confront him, but get turned against each other, and disband.
C.I.A. Agent Nick Fury visits Reed, his old Army pal, to enlist his aid against the Hate Monger. Fury schemes to separately send each member of the Fantastic Four to the Hate Monger's South American base, where they reunite and confront the madman. The Hate Monger is killed by his own men, and is revealed to be Adolf Hitler (or a body double).
Reprinted in Marvel Collectors' Item Classics #15.