Depends on where you live, in Europe Messi is very well known for example, Lebron I've never heard of, Zuckerberg is known by people in tech and maybe some othe

Depends on where you live, in Europe Messi is very well known for example, Lebron I've never heard of, Zuckerberg is known by people in tech and maybe some others. I'd bet on some singer or actor / actress being the most well known globally. There's always a possibility that it's some Chinese / Indian person that is completely unknown outside their own country, but because of that country's size still ends up "the most well-known"