You are Traveler!
Along the course of the initial adventure, the Traveler will learn how to use Anemo and Geo elements. This makes them unique, since other characters can only use one element. Future updates to Genshin Impact will supposedly allow the Traveler to learn how to use all the other elements, until all of them have been acquired.
Additionally, the Traveler is incredibly powerful. Their base stats are good, but their character progression tends to be better than the other starters’. This is why the Traveler usually ranks as an A-tier character on Genshin Impact character tier lists. As the protagonist, the Traveler is just more powerful and offers more playstyle flexibility than the other free starter characters.
Because they are capable of learning other elements, the Traveler will only get stronger as Genshin Impact gets more updates. Even initially, though, the Traveler is stronger than Genshin Impact’s other free starters characters. Because of this, the Traveler is easily the best free character in Genshin Impact.