When Captain America gained the gamma powers of the Hulk, he became a towering monster capable of going toe to toe with Bruce Banner's alternate form. However, while Cap's transformation was as monstrous as fans might imagine, it actually broke all the rules surrounding Hulk's powers and the way in which they manifest.
At the time, the man wielding the shield was Bucky Barnes — the former Winter Soldier — who had taken over Steve Rogers' superhero identity following his apparent death. While he didn't have the benefit of the Super-Soldier serum, Bucky gained near-identical powers from the Infinity Formula, which added to his existing cyborg enhancements and years of training, first as Steve Rogers' wartime sidekick, then as an assassin for Russia's secret Red Room training program.
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It was in his role as the new Captain America that Bucky — in Jeph Loeb and Ed McGuinness' Hulk #21 — was part of a mission to stop the Red Hulk and the villainous Intelligencia, instead being bathed in radiation that, like Bruce Banner before him, turned him into a gamma mutate. Like most of the other heroes affected (including Captain Marvel, Cyclops, and the Human Torch), Bucky grew to a Hulk-like size, gaining super-strength, incredible durability, and a Hulk-level healing factor. Bizarrely, his prosthetic arm was somehow similarly affected, swelling in size and sprouting spikes. While Captain America's shield was no longer needed as protection, Bucky-Hulk was able to wield it as a weapon, even almost bisecting the similarly bulked-up Wolverine.
What's strange about this transformation — and the others that occurred alongside it — is that it's so out of step
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