The Avengers and Fantastic Four are two of the biggest supergroups in Marvel Comics, whose adventures have spanned decades. Rarely has either team lost a fight resulting in the death of their entire respective teams. However, in a mid-'90s comic, the Avengers and Fantastic Four were both entirely wiped out by the same enemy.

The character Onslaught first appeared in the pages of X-Men as a sentient entity created from the consciousness and dark psyche of both Charles Xavier and Magento. Onslaught was overpowered and had the goal to wipe out humanity. Mutants didn't have much of a chance against the villain, as he became more powerful with each of their attacks. However, when the Avengers and Fantastic Four joined the fight, things turned deadly.

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Black Panther, Thor, Iron Man, Ant-Man, Hulk, Captain America, Falcon, Vision, and Scarlet Witch were among The Avengers who teamed up with the Fantastic Four (and the X-Men) in an effort to end Onslaught's quest for supremacy. Jean Grey suppressed the Hulk's alter-ego to make him even more filled with rage, leading him to rip Onslaught's armor off. Without a physical form, Onslaught used Franklin Richards to form a second sun. Knowing the sun would kill everybody in New York, the two groups sacrificed themselves to stop the destruction.

Onslaught defeated Wolverine

In the comic, Thor charges at Onslaught's energy form. Meanwhile, the Avengers and Fantastic Four sacrifice themselves by entering the energy field which destroys Onslaught's remaining energies. The ensuing rift seemingly killed the heroes. The day is saved at the cost of the heroes' lives... or so it seemed.

It wouldn't be a comic book if the sacrifices weren't immediately undone. While it's initially believed both the Avengers and Fantastic Four teams were killed at the moment, it's later revealed that Franklin created a pocket universe for the heroes until they made their way back. It's in that pocket-universe, called Counter-Earth, where Rebecca "Rikki" Barnes first debuted. The heroes would all make their return to their reality in Heroes Reborn: The Return #4. 

The Avengers and Fantastic Four will never stay dead in the comics. The characters are simply too popular to be put to rest for good. While the Onslaught saga was poorly received, it showed that Marvel's greatest heroes are willing to sacrifice themselves for the greater good. They proved what being a hero is all about. The Avengers and Fantastic Four feature some of the bravest heroes in all of comics.

Next: Marvel's Avengers Just Created a Hulked-Out [SPOILER]