I find it unfortunate that the label "The One" is used ambiguously. We have the quest "Proving Ground" which provides the trophy "The One", it is a championship like Driftwood champion. it is an arena fight, sort of. Then, there is the other quest "Arena of the One" which means the one player that shall reach divinity, fighting other story characters. But you do not have to have the "One" championship title, it is unrelated, two different things. Just writing this for folks that might be confused. I think also in the lore the "One" is used wishy-washy.