Pretty much any successful, lasting artist worked hard to get to where they are. They have different stories and have different types of hardships, but it isn't easy to get to where these people are.
Bey ofc. Her parents had to quit their jobs and downsize so they could focus on DC and Girls Tyme. Not mention they had gotten dropped before then, had to audition for their record deal. The DC debut album wasn't very successful but Bey preserved and found success. A true hero tbh.
Beyonce probably had the easiest upbringing of any pop girl ever tbh. Most pop girls struggled with poverty or abuse or depression or other things of that nature in their early years while she had a very priveleged lifestyle for the most part. Not to mention, the strong influence of her father to help guide her and protect her from things other females in the industry have been subjected to gave her an advantage most people didn't have
JLO and Madonna both came from very humble beginnings with very little money, but I think I'd give the edge to JLO, because she was able to work her way from being an actress into having a full blown music career and not many people (if any) have been able to make that kind of transition into maintaining dual careers the way she has