Both Cristiano Ronaldo and Brazilian Ronaldo are extremely famous.
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culture
Chinese fans disambiguate with 大罗 (Ronaldo Nazário, 'Big Ronaldo', Brazilian striker and 2002 World Cup star) vs 小罗 (Ronaldinho) vs C罗 (Cristiano Ronaldo, Portuguese). Just saying 罗纳尔多 without a prefix usually means the Brazilian Ronaldo.