Despite how heartwarming Asami and Korra's first meeting was, it was sad they were unable to meet again.
The scene with Asami's mother was heartwarming, but it is sad knowing what will become of her later.
Chapter Two: Escape to Republic City
It is clear that Korra's time with the Red Lotus was far from an ideal upbringing.
Chapter Three: The Missing Child
Senna fearing that Tonraq would accuse her of cheating on him when Korra begins firebending. Luckily, that did not happen.
The story of Korra being kidnapped by the Red Lotus.
The fact that Senna and Tonraq were unable to have another child after Korra was kidnapped leaving them childless for fourteen years.
Chapter Four: First Meeting
Korra's first night in Republic City during which she gets lost, falls asleep on the street and wakes up only to get attacked by a gang.
Chapter Five: Adventures and Misfortunes
Mako telling Asami about his past.
Mako: You don't get it at all, do you? Me and my brother, we've been orphaned for years, and there was nobody willing to look after us. We had to survive on our own, doing whatever we could to survive. Sure we can both bend, but no company wants to hire kids. The gangs aren't so picky; some of them can use kids with those talents. And not for anything good. But it was a choice: Work for the gangs or starve in the gutter. At least our gang gave us protection from my parent's killers. The police lost interest real quick. And I can't just walk away from it now. Not while my brother still needs me.
Chapter Six: Memento
Flashback to Korra being successful kidnapped by the Red Lotus and being told her parents are dead.
Korra: Where are we going?
Zaheer: The North Pole.
Korra: I...I want to go home now...I want my mommy and daddy.
Zaheer: You will be home soon.
Korra: I will?
Zaheer: Yes. But it is not the same home. Korra, I am so sorry, but your parents are gone.
Korra: But... but they'll be in the hut. Sometimes Daddy goes away, but he always comes back. He always comes back. And Mommy will be there now. She's always there.
Zaheer: Not this time. They can no longer take care of you. Something terrible happened to your home and we need to keep you safe. I'm sorry, but you cannot go back.
Korra: (beginning to cry) But...but I want to.
Zaheer: I know this is a difficult time, and this is a shock. But we cannot let you go back. You are too important. We will keep you safe until it is the right time. Korra?
Korra: (shaking) Uh-huh?
Zaheer: I must apologize. I did not start this conversation in quite the right way. My companions and I will be your protectors and your teachers. We will be your new parents.
The fact that Zaheer was lying about the Red Lotus being parental figures and putting her through a Training from Hell regiment for fourteen years.
Chapter Seven: Search of the Lotus
Ming-Hua proving to be a textbook Sadist Teacher by brutally killing an Otter Penguin in front of a child Korra.
Korra's breakdown after Ming-Hua's ice tentacle demonstration, along with Ming-Hua's complete Lack of Empathy.
Zaheer elaborates on his brainwashing of Korra.
Chapter Eight: The Chiblocker Lady
The fight against Shady Shin's gang ends up costing Mako and Bolin their home.
Chapter Nine: Uncharted Territories
The fate of Naga's mother.
Chapter Ten: Connection
Zaheer paralyzes Korra and was going to leave her alone in the snow had it not been for Ghazan and P'Li intervening.
Korra: "Zaheer, I'm...cold. Don't leave me out here. Please?"
Korra at first being unsure of how to respond to Asami's hug due to having no memory of ever being hugged before.
Narration: Korra was not sure how to react to this. After a delay she lifted her arms and let them settle around Asami. That seemed to be okay.
When Bolin is looking for the best spot to put the photograph of his and Mako's parents.
Bolin: I need somewhere to put this.
Mako: Near the kitchen. (quietly) They both loved cooking.
Chapter Twelve: City of Fireworks
This chapter really illustrates how much of a Fish out of Water Korra is in terms of anything outside of training with the Red Lotus.
Chapter Thirteen: The Game
While the party celebrating the Fire Ferrets' first victory was heartwarming, the mood is immediately soured by the Red Lotus' arrival.
Chapter Fourteen: Terror
This chapter illustrates how messed up Korra's psyche is after being raised by the Red Lotus all her life since she felt the need to apologize to them for running away despite feeling imprisoned by them and the fact Zaheer struck her face.
Asami feeling powerless as Korra is being kidnapped right in front of her.
Korra's farewell to her friends.
Korra: Asami? Mako? Bolin? This is goodbye. Thank you for... everything. Don't follow me, don't look for me; just let me go. I have to do this. So; please take care of Naga.
Mako: Asami? Do you know something? Did Korra say something about this to you?
Asami: No, but... (sighs) I never wanted to be right. If I was right, then I never told anyone, and then... all this would be my fault. (bitterly smiles) So, I guess it really is my fault in the end. I could have stopped it years ago.
Chapter Fifteen: Assassination
Pretty much the entire last half of the chapter is this for Korra.
Chapter Sixteen: Broken Chains
Korra believing that her friends would not want to have anything to do with her after she left with the Red Lotus.
Chapter Seventeen: Korra's Decision
Korra and Asami blaming themselves for what happened.
Mako and Bolin's farewell to one another when they think they're about to drown.
Mako: Water really was the death of me, huh? Pretty unremarkable way to go. Not quite what I would have had in mind. Least of all having it happen with you. You're supposed to outlive me...Sorry I couldn't protect you. I love you.
Bolin: I love you too, Mako.
Chapter Eighteen: Rebellion
Earlier Senna expressed horror at the idea of her daughter becoming a killer. While she killed several members of the Red Lotus in self-defense, it does not change the fact Korra became what her mother feared.
Asami nearly dying.
Chapter Nineteen: Freedom
While Korra's reunion with her parents was heartwarming, there is a strong sense of awkwardness along with how they all blame themselves for what happened. Senna even sadly admits they can never get the time they lost back.
Book Two: Metal
Prologue: Katara's Story
Katara's conversations with Korra's friends are a mixture of this and Heartwarming.
Korra is suffering a Heroic BSoD following the events of Book One.
Chapter 39: Crystal Catacombs
The massive Downer Ending we are left with: Amon is killed and the Equalists are stopped, but Ba Sing Se is in chaos, Mako (and possibly Bolin) are dead, Korra has lost her bending, Asami has just about lost everything she once had, and Kuvira is shaping up to be the main antagonist of Book 3, playing everyone for fools and tools like the Well-Intentioned Extremist she is in canon.