The first Giganto seen was one of the mutates created by the Deviant scientists to serve as part of Kro's invasion force when gathered on Monster Island.

[1] The Mole Man unleashed Giganto upon the surface world to attack and destroy chemical plants in the Union of Soviet Socialist Republics, Australia, South America, and French Africa.

[5] When he believed that the Avengers were the ones responsible for destroying part of his kingdom, he unleashed Giganto and other mutates to attack Los Angeles.

[8] The Inorganic Technodrone was finally found by Giganto's mate who had laid on the flying saucer containing it thinking it was a nest.

[9] Mole Man, Giganto, and Tricephalous were conjured from the timestream by Aron the Rogue Watcher to oppose allies of the Fantastic Four who have come to prevent him from creating a pocket universe.

[10] Mole Man assembled Giganto and other monsters to invade the surface only for it to be abandoned when the Fantastic Four were discovered to be alive.

[16] Later, Doctor Doom had one of his servants steal the Horn of Proteus awakening a larger Giganto and a number of sea monsters to attack a New England town.

[19] In a plot to assist the Human Torch and Anne Raymond, Namor disguised himself as the Mad Thinker and unleashed a robot version of Giganto.

[20] As a plot to ruin Namor, Llyra and Llyron used the Horn of Proteus to awaken Giganto and sent him to attack the UN Building.

[23] Namor sent Giganto and other sea monsters to an uncharted island to make sure no one interferes with the honeymoon of Ororo Munroe and T'Challa.

[24] In the storyline Fallen Son: The Death of Captain America, Tiger Shark used the Horn of Proteus to summon Giganto and other sea monsters to attack the city.

[26] The Deviant Mutate version of Giganto has vast physical attributes, the ability to dig underground, and hold his breath underwater.

The Atlantean Beast version of Giganto has immense strength, resistance to injury, can adapt itself both underwater and on the surface, as well as shooting water from its blowhole.

In the "House of M" storyline, the Deviant mutate version of Giganto was killed by Doctor Doom's Fearsome Four alongside Mole Man.

[volume & issue needed] In JLA/Avengers, the Deviant mutate version of Giganto was among the monsters who fight the Justice League in their search for the Ultimate Nullifier.

[27] Namor later mentions the Atlantean Giganto, comparing the effects of Aquaman's marine life telepathy on a half-Atlantean like him as feeling like his head had been crushed by the beast.