Together with Moth-Godzi and Bio-Godzi, this is one of my three favorite versions of Godzilla.
As others pointed out, the huge mass (and I'd add, the long and powerful tail), along with that gigantic range of dorsal fins, give Kin-Godzi a very powerful look. I actually love the way different angles provide contrasts. When sighted just offshore from the NATO base, he looks almost unearthly: there's something about his bulk and strange head that visually drive home the point that this is a mutated horror unlike anything humanity could have imagined. I think if I'd been serving at that base, heard the sirens, looked out in the water and saw THAT, I would have needed to change my uniform.
From the side, Kin-Godzi's head looks distinctly reptilian, more so than in any other film: almost like a savage and immensely powerful snake.
Then there are the subtle but welcome touches, like the fact that his fins glow before he unleashes his atomic breath (as in '54), and the variations in his roar: all of which sound even more nightmarish than in the original film.
Finally, the fact that he is literally head and shoulders taller than his opponent conveys just how hopelessly outmatched Kong is for most of the film.
For a few moments in Godzilla X Megaguirus, when Godzilla is seen from the front, coming ashore on the island, he almost looked like Kin-Godzi, back from the 60s... and that would have been more than fine with me.
"Rudeness is the weak person's imitation of strength." -- Eric Hoffer