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.

I asked AI Aliens are they real ?

There is no scientific evidence to suggest that aliens, or extraterrestrial life, exists. While it is certainly possible that there may be other forms of life in the universe, the question of whether or not aliens are real remains a topic of debate and speculation. Many scientists believe that the conditions necessary for life to arise may be rare, and that the chances of there being other intelligent life forms in the universe are relatively small. However, some people believe that there is strong evidence of the existence of aliens, and that the subject warrants further study and investigation. Ultimately, the question of whether or not aliens are real is a matter of personal belief.