This stock doubled in 2023, and it's still gaining.Fintech, or financial technology, has exploded as a global industry. The ability to move money electronically at lightning speed has changed the way the world does business and people consume. As with every industry, there are leaders and laggards. If you're interested in a top fintech stock with vast opportunities, consider Nu Holdings (NU -3.14%).New to youU.S. investors may not be familiar with Nu because it operates, under the banner of NuBank, in Latin ...