(I asked for my account to be deleted, to spend more time advertising for my business, but since it is still here and this was a hell of a chapter, I will comment..)
Jaygarcia Saturn is actually, legitimately intimidating. For one thing, his appearance/transformation on the island was very reminiscent of Luffy's Gear 5, just his presence alone made such a scene. Then you add this scene the head of a marine looking at him exploding, with no explanation whether that is a subconscious effect or willful exertion of Saturn's power. But adding to the fact is that he is of an absolute unknown quantity. We don't even know for sure yet if he is a devil fruit user, an actual demon, or what.
The only feat to scale him is Bonney stabbing him and some argumentation might be made to mock Saturn - no future sight - but who knows if he just instant regens the next chapter.
My whole point is this. The beauty of this scene is the introduction and the lack of information itself. This is the right way to portray a character as intimidating.