I still haven't seen season 4 till this day. I heard some people hate it because Korra and Asami became a lesbian couple out of nowhere.
They started building their relationship in Book 3, and made the foreshadowing that they were developing feelings for each other more prominent in Book 4. You could argue that more could have been done to make it obvious, or that it would have been more rewarding to have them in a relationship during the show rather than showing them beginning their relationship at the very end of the show. But the people who reply with 'oh well that just means they're good friends' when you point out to them examples of said foreshadowing are exactly the kind of people you'd expect to wail and gnash their teeth against something like this. ---
Simple questions deserve long-winded answers that no one will bother to read.