According to the film's director, Godzilla vs. Kong’s Hellhawks were originally meant to be nearly as big as Godzilla and Kong. The Hellhawks are just one of the many Titans seen during the Hollow Earth portion of the film, when Kong and his human allies journey back to his species’ ancestral home. The Hollow Earth Titans didn't get much spotlight in the final cut of Godzilla vs. Kong, but the Hellhawks were apparently a lot more dangerous in early versions.
A large number of Titans have been featured on screen since the MonsterVerse began with 2014’s Godzilla. Some of those have been classic Toho Kaiju like Mothra, Rodan and King Ghidorah, but many more are entirely new monsters created for the Legendary franchise. These include Titans like the stone golem Methuselah, and the giant spider Scylla. 2014's Godzilla centered on the new MUTO monster, but Godzilla: King of the Monsters gave the spotlight to more famous Kaiju.
However, it seems Godzilla vs. Kong’s Hellhawks were originally conceived as more direct villains. During a recent Reddit AMA, Godzilla vs. Kong director Adam Wingard discussed the Hellhawk design, revealing that the Titans were initially planned to be almost as big as Godzilla and Kong. He also shared that Kong had a big fight with the Hellhawks in an earlier version of the script but that the fight was removed for streamlining purposes. Read Wingard’s full quote below.
“We always called the Hellhawks YOSHUMA while in production. Originally they were nearly as big as KONG and I believe he fought some in an early draft of the script. Eventually we shrunk down and repurposed the design for the version in the film. This isn't a very interesting story but to be honest I just wanted a reptilian owl creature in Hollow Earth. Images of the original design should be in the making of art book.”
Even in their reduced size, the Hollow Earth Hellhawks are still frightening creatures, somewhere between, as Wingard says, a massive lizard and a bird of prey. They’re just one example of the immense otherworldly detail present in the Hollow Earth, which helps make it one of the best parts of the film. There are still no official plans for another MonsterVerse film to follow Godzilla vs. Kong, but if a sequel is made, it will hopefully spend some more time within the Hollow Earth itself. After such a strong introduction in Godzilla vs. Kong, setting more stories within the Titans’ home could be a great move for the future of the franchise.
While it would have been fun to see an even larger version of the Hellhawk design in Godzilla vs. Kong, it wouldn’t necessarily have made a lot of sense. The Titan history revealed in the movie shows that Godzilla and Kong’s species were clearly the dominant rulers of the ancient Titan world, so introducing new monsters of equitable size and strength would be a bit odd. Of course, there might be other Titans that could challenge the kings of the monsters, hiding somewhere in the Hollow Earth while they wait for the right moment to emerge. If the MonsterVerse continues past Godzilla vs. Kong, new and more dangerous Titans will likely be revealed.
Source: Adam Wingard