The fact that Korra and Asami are best friends is gloriously ironic, and I love it.
You have the non-bending daughter of an Equalist who wanted to eradicate benders completely paired with the Avatar herself, the only person who can not only bend one element, but all four. Asami is Chief Executive Officer of the company that once played a major role in Korra’s near assassination.
Not only that, but since both of them found themselves being pulled into a competitive love triangle situation (the age old “they both dated the same guy basically at the same time” position) they’d naturally be made up as rivals. But instead of fighting over the guy, the two became closer for it and turned that trope on its head.
For both of them, their friendship is their closest non-familial human relationship (and in the current canon, it’s the closest relation we see Asami have with anyone).
Their enemy status seemed almost predetermined, but with maturity, kindness, and a lot of natural compatibility, they pulled off a remarkable and supportive friendship. I think that’s amazing.