Aang 100 percent

It's a little unfair, since Aang was naturally very spiritual from his upbringing.

I think Korra, since she had the most knowelge about it and avatar wan and stuff

those who vote for Aang are robots who do it automatically. because for the entire series, not a single example of aang's spirituality is shown, at least at the level of the korra of season 2, I am silent about 4.