I am so grateful that LoK never had Mako acting like a bitter ex, just as much as I’m delighted that Korra and Asami didn’t jump at each other’s throats and rather did at each other’s arms.
Thing is, there’s something very beautiful about how this three characters were handled.
When Mako and Asami broke up, it was because, even if they worked together, he loved someone else and Asami was fierce and independent enough to walk away from someone who wouldn’t love her fully. Even when they got back together briefly, they kept drifting away because of his conflicted feelings.
Then, even if Mako dumped Korra during an argument, at the end they both talked things out and came to the conclusion that, even if they loved each other, things wouldn’t work out between them and Korra was fierce and independent enough to walk away from a relationship without future.
So we have three people who have come to acknowledge that things will never work out that way between them. And what happens? They are mature enough not to let it destroy their friendships.
Mako is, correctly, ashamed of how he treated them and slightly terrified of the power this two ladies hold within their friendship; but he also ultimately deeply cares about both of them, and even if he’s resigned to the idea of a romantic relationship with either, it is clear he still has strong feelings for Korra who, however, has moved on.
And Asami and Korra, two awesome strong ladies who were confident enough to walk away from wrong relationships and wait for the right one… without turning it into a girl fight.. found in each other exactly what they needed. Love and understanding. They built a solid foundation and finally found in each other a strong balanced relationship. They found fulfillment and happiness in one another.
This is why their ending was so perfect for a book titled Balance. Because the other two books had done such a perfect work showing us the other two unbalanced sides of the trio… And finally demonstrated that Korra and Asami were perfect for each other.