I do love how Korra and Lin initially are like grrrrr at each other (Lin at Korra for her aggressive behaviour, and Korra at Lin because she hates being told what to do) but later come to deeply respect each other and form a close bond.

I don't know if you remember this moment but... near the end of season 1... I was honestly quite emotionally moved by the point in the story where Korra is waterbending herself out of the pro-bending arena to give chase to Amon's henchmen as they escape through the hole in the roof on the airship - but she can't blast herself far/high enough, and doesn't quite reach, and then the look on her face as she thinks she's failed, and she begins falling back into the arena and then BAM Lin has thrown one of her metal string/rope (whatever they are) things out and catching her, swing her and then propels her back up so they reaches them.

And of course when Lin is captured and won't tell them anything about Korra. (and how Lin is willing to sacrifice herself to allow Tenzin's family to escape).

However, in terms of a direct mentor, I do think Tenzin (the calm mink-like spiritual leader [even if he is prone to a few grumpy outbursts]) is a better person to balance Korra and her temper as she becomes frustrated with her learning. I think he was good for her, and I also loved the moment when she admitted [probably for the first time in her life] that she was afraid (I think the line is 'I was so scared') and then just hugs him and cries as they kneel on the floor on avatar island.

Yeah, I like this show too much!!!!