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.

Did Melania Trump change after she married Donald Trump?

 It is difficult to say for certain how a person changes over time, as people's behaviors, attitudes, and personalities can evolve for a variety of reasons. Without more information, it is not possible to accurately assess any changes that may have occurred in Melania Trump after she married Donald Trump. It is important to remember that people are complex and multifaceted, and it is not appropriate to make assumptions or judgments about someone based on limited information.