There is no single "best" fintech company, since there are many different types of financial technology companies offering a wide range of products and services. Some fintech companies specialize in payments, others in loans and lending, and still others in financial data and analytics. So it really depends on what type of fintech product or service you're looking for as to which company would be the best fit.
There are a few fintech companies that are generally considered to be leaders in the space, such as Square, Robinhood, and SoFi. Square is a payments company that offers point-of-sale software and hardware for businesses, as well as a suite of financial services for individuals and businesses. Robinhood is a popular stock trading platform that offers commission-free trades and has been expanding into other financial products like savings and loans. SoFi is a lending company that offers student loan refinancing, personal loans, and other financial products.
There are many other great fintech companies out there, so it's really worth doing some research to find the one that best meets your needs. You can check out websites like Fintech Zoom and TechCrunch to find articles and reviews about different fintech companies, and compare their offerings to see which one would be the best fit for you.