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.

How did Han Xin become a great general in the Three Kingdoms era?

 Han Xin was a military general who lived during the Three Kingdoms period in ancient China. He is known for his strategic and tactical skills, as well as his ability to inspire and lead his troops. Han Xin rose to prominence through a combination of hard work, determination, and natural ability. He began his military career as a common soldier, but quickly distinguished himself through his courage and intelligence. He was eventually promoted to the rank of general and became a key figure in the conflict between the three rival kingdoms of Wei, Shu, and Wu. Han Xin's greatest achievement was his victory at the Battle of Pengcheng, where he defeated a much larger enemy force and helped to establish the Kingdom of Han. Overall, Han Xin's success as a general was due to a combination of factors, including his personal abilities and the opportunities that were available to him at the time.