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.

Which sector gives the highest return?

 It is difficult to determine which sector consistently gives the highest returns, as the performance of different sectors can vary greatly over time. In general, the stock market has the potential to provide higher returns than other investments, such as bonds or savings accounts. However, the stock market is also more volatile and carries more risk, so the returns on individual stocks or the overall market can fluctuate greatly.

Some sectors, such as technology and healthcare, have historically outperformed the broader market and provided higher returns for investors. However, it's important to remember that past performance is not a guarantee of future results, and the best performing sectors can change over time. It's also important to diversify your investments across different sectors and asset classes to spread out your risk and potentially improve your overall returns.