I was totally OK with all three ending scenarios. At the beginning of this book, you could find yourself rooting for Alina to save the Darkling (or turn dark herself), Alina with Nikolai, and Alina and Mal (even if this was set up from the beginning).
Alina is far from the perfect heroine. In the first book, she’s very naive (though I loved her sarcasm). Since, though, she was forced to grow up, though she continually fights through so many weaknesses.
But back to the ending, I gotta say I think Leigh Bardugo did the right thing, there was no other truly appropriate endgame here.
It will be interesting to view the series on Netflix which starts in the next few weeks.