Was Crocodile stronger at Marineford? Or was he holding back in Alabasta?

 During the Alabasta arc, Crocodile displayed a level of power that was initially considered overwhelming by the Straw Hat Pirates. He possessed the Logia-type Devil Fruit called the Suna Suna no Mi (Sand-Sand Fruit), which granted him the ability to control and transform into sand. He had a reputation as a Shichibukai and controlled the desert kingdom of Alabasta from the shadows. His strength was showcased through his battles with Luffy and others. At Marineford, Crocodile was present as part of the war that took place at Marine Headquarters. While he did participate in the battle, he didn't display the same level of dominance as some other powerful characters present. This has led fans to speculate that he might not have been as strong as initially portrayed in Alabasta. It's important to note that power scaling and character abilities can be subject to interpretation and development by the author. Oda often keeps details deliberately open-ended to keep the story intriguing.

Is nominalism quantum mechanically verifiable?

 Nominalism is a philosophical position that denies the existence of abstract objects, such as numbers or universals, and holds that only concrete objects exist. Quantum mechanics, on the other hand, is a scientific theory that describes the behavior of physical objects at the quantum level, including atoms and subatomic particles.

It is not directly relevant to consider whether nominalism is quantum mechanically verifiable, as nominalism is a philosophical position and quantum mechanics is a scientific theory. However, it is possible to consider how the principles of nominalism might be applied to the interpretation of quantum mechanics.

One approach to interpreting quantum mechanics, known as instrumentalism, takes a nominalist perspective and views quantum mechanical theories as merely a set of mathematical tools for predicting the outcomes of experiments. From this perspective, the abstract concepts of quantum mechanics, such as wave functions and superpositions, are not considered to have any ontological (i.e., real) existence, but rather are simply useful mathematical constructs.

Overall, while nominalism and quantum mechanics are not directly related, nominalist approaches to interpreting quantum mechanics have been proposed and continue to be an active area of philosophical debate.