Diamante can barely flutter the surface of a minor plateau. Good luck in him fluttering massive mountains of rocks(in terms of size and volume) that Pica showed the capacity to level up. He also lacks the scale and power in his swordsmanship move. While his "half moon" attack displayed in this chapter was relatively impressive, not only it requires a little prep time, but infront of the giant, the slash won't really maneuver too deep and far. His best chance would be to dodge.
However with Pica's complete control over the ground environment, he can easily block Diamante into a specific location by manipulating the ground environment and why not taking advantage to also destabilize his balance, while creating some mini golems and smash him into pieces(and considering the little prep time of his moves, he won't manage to counter them all in time, if even one of them).
Also, for Senor Pink to actually catch Pica inside the rock with his ability, he actually has to make it to Pica first, so knowing his exact location(who can anywhere in the rock) and actually catch him all that before Pica can switch location(he has night instantaneous transport inside rock). Meanwhile, Pica can use the rock environment to burry him in the stone or simply cut him into multiple pieces with the amount of bladed weapon he can take around the environment with his superior combat ability
And defensively, he is difficult to beat with the night instantaneous rock regeneration through environmental rock assimilation. You will have to go through a massive amount of rock even before trying to catch his real body(assuming you even know his real location), something not even guaranteed considering he can instantaneously switch from one place to another(from afar) without you realising
Pica really has the capacity to solo this if he plays his cards right. No wonder he seemed so confident in his power relative to the rest of his family. Gladius as well has been portrayed as the strongest executive and his attacks frankly speaking are even comparable to Diamante's in terms of scale. With Gladius ground bombs implantation, in combo with Pica's environmental alteration, it can easily be a deadly combo. Baby5 and Buffalo also showed great teamwork and are the ones Doffy actually chosed for the external mission to recover Caesar. It's funny in the end how it's Pica's division that showed the best amount of teamwork and good combat abilities with only Lao G and Dellinger clearly competing in the area
