Season 3 introduces the city of Zaofu in the Earth Kingdom that was founded by Metalbenders. It consists entirely of clusters of palace-like buildings in the shape of flowers, all made out of stainless steel, and during nighttime the benders close their "petals" around them.
Schizo Tech: Despite the generally Early-Twentieth Century level of technology present in the show, the Equalists seem to have mastered high-energy, low-mass power generators or batteries, giving their mooks electrified Kali-sticks and Power Palms. This is specially surprising taking into account that the city uses lightningbenders for power generation.
Scooby Stack: In "The Guide", we get a rare two-sided one, as Kya, Bumi, Pema, Jinora, Meelo and Ikki all peep in around the edges of a doorway on Tenzin admitting that he has never been able to make it to the spirit world.
Screw the Rules, I Have Money!: The Wolf-Bats pay off the referee in the pro-bending Championship so they can cheat without being called on it; by their third round with the Fire Ferrets, it is so blatant that the announcer calls them on it. It's implied by Amon that this is hardly unusual for them.
This is also true of Varrick, who is using his money to nefarious purpose, but is still a respected figure.
Senseless Sacrifice: In "Turning the Tides," Lin stays behind to hold off the Equalists and gets her bending removed. In "Endgame," we learn that the Equalists managed to capture Tenzin and his family anyway and are planning to remove their bending at a mass rally.
Sex Sells: After essentially inventing silent films (or reinventing them into talkies), what is the first thing Varrick decides to do with it? Get the hot chick to pose for the camera.
Shame If Something Happened: Varrick does this to Mako, stating it would be a shame if something happened to Asami or Bolin. When Mako refuses, he frames Mako for the robbery of Future Industries.
Asami, who subverts all the romantic rival and Woman Scorned plots and every single stereotype associated with her position. Notably, she's a wealthy, beautiful heiress who turns out to be great at fighting, a savvy businessman and engineer, a skilled race-car driver, and also unfalteringly kind and sweet. When her father's revealed to be an Equalist, she not only refuses to join, calls him out for letting his grief justify a vendetta, and almost a year later cheerfully refers to him as "diabolical".
Suyin Beifong. With her troubled past and her admitted harbouring of pirates, traitors, and conspirators within her city, you would expect her, as Lin does, to be hiding something, even to be linked to the Red Lotus. And you'd be absolutely wrong! Turns out her redemption story is as honest and true as can be.
Shell-Shocked Veteran: While she might not have fought in a war, Korra has this reaction after her battle with Zaheer. She has trouble fighting, and is constantly haunted by a vision of herself following her around the world.
Shoo Out the Clowns: Averted with Naga. Bolin tries to protect Naga and Pabu by telling them to stay put away from the fight in the two chapter finale; turns out Naga and Pabu save Asami and him when they get captured and that Naga is quite the fighter.
"The Aftermath" also features a brief racing segment, set to music that's similar to the Speed Racer theme.
Varrick's motion picture from "Rebel Spirit" is a Avatar-verse version of "Sallie Gardner at a Gallop".
Varrick later creates the Avatar-verse version of Nanook of the North, "Nuktuk, the Hero of the South", with Bolin in the lead role. It's remiscent of 30s sci-fi serials like Flash Gordon while doubling as pro-South propaganda. Further, its title puns on Nanook of the North, a classic "documentary" on the Inuit (of whom the Water Tribe are a partial Fantasy Counterpart Culture).
A number in the Beginnings episodes out to Hayao Miyazaki films. Spirits have a procession towards a hot spring and the disguised human is found out by smell. Wan rides a deer-like creature while trying to stop humans and spirits from killing each other. Remind you of anything?
Continues in "A New Spiritual Age", where Korra has her age changed and finds that her emotions, especially strong ones, can influence her surroundings in the Spirit World, similar to Sophie in Howl's Moving Castle. She also rides a dragon she rescued, like Chihiro in Spirited Away.
At the same time, a little girl wanders about a fantastic world of unusual geometries with talking plants and animals, including in a significant tea party full of Cloud Cuckoolanders? Are we talking about Korra or Alice?
A few of them also look like Pokémon and "mushi"; the green No-Face expy's flat face is similar to a character from Rice Boy.
Sealed Evil in a tree, thanks/no thanks to the hero: Korra: Vaatu, evil spirit of chaos, freed from his fight with Raava, good spirit of peace by future first Avatar Wan who then re-sealed him in a dead tree in a desert in the spirit world —> Samurai Jack: Aku, evil spirit(?) of greed, sealed in a dead tree in a swamp, unsealed by Jack's dad —> Ferngully The Last Rainforest: Hexxus, evil spirit of pollution, sealed in a dead tree in a wasteland, accidentally unsealed by woodcutter Zak.
The kaiju-style battle between Korra's spirit and "Vaatuunalaq" is like a cross between Evangelion Vaatu/Unalaq looking really angel/Eva-y vs. a giant blue woman and Paprika the heroine's dream-self becomes huge to battle her mentor-turned-evil before he can throw the world into chaos.
Wan is introduced like Aladdin: a thin young man, having just stolen a loaf of bread, is running through the city streets chased by well-armed fat men.
When Bolin faces off against Northern terrorists (actually Varrick's hired gangsters), he is accompanied with a triumphant Eagleland-esque fanfare, as he tears off his sleeves - good thing Bolin eats his spinach!
Immediately following this scene we have Mako being released from prison, greeted by a crowd of admirers, and told by his boss that he has been promoted to detective, while Lu and Gang have been fired. The dialogue in this scene is very similar to the ending of Mulan.
Tonraq saying he had been running from the past for so long in Civil Wars part 2 is similar to what Simba from The Lion King said.
When Vaatu fires his purple beam, both the beams effect and the way Vaatu stands is eerily reminiscent of the Reapers from Mass Effect. Vaatu even looks a little like a Reaper when he prepares the beam for the first time.
In the episode "Harmonic Convergence", Bumi's destruction of the Northern Water tribe's base via a mechatank gone haywire is reminiscent of Major Frank Burns' out-of-control camp-trashing tank joyride in the M*A*S*H episode, "Hey Doc".
Tenzin has this relationship with his siblings Kya and Bumi. When they were children. Tenzin was very serious while his siblings were rather rambunctious. In the present we've seen that Tenzin is serious (usually), bald, and monk-like while Bumi is "a wild man" in the armed forces of the United Republic with a head full of anime hair; meanwhile Kya is unmarried and traveled all over the world to "find herself" (which Tenzin saw as abandoning her family) while Tenzin settled down and had a large family. Tenzin and Kya are benders with a spiritual/healing, while Bumi is a Bad Ass Normal military man/walking disaster area.
Sickeningly Sweethearts: Mako and Asami are too much for Korra to handle, although her own feelings for Mako probably contribute.
Sigil Spam: Once you see it as the Season 4 trailer emblem, you can see the Metal Clan symbol everywhere in the Zaofu scenes in Season 3.
Sliding Scale of Villain Effectiveness: High. The Equalists present a formidable threat to the Avatar and Republic City. Neither Korra nor the city's official police have been able to stop Amon or his agenda until their ultimate defeat in the season finale.
Same for the spirits of season 2: they can shrug of all but the most powerful bending and it takes special bending altogether to purify and/or turn them. Their leader is even tougher and they come very close to winning forever.
The Red Lotus of season 3 uphold up the trend by being exceptionally good at both combat and strategy; in fact, even though they're also defeated at the end of the season, one of their main victories remains completely unreserved; the plunging of the entire Earth Kingdom into anarchy. Their leader is also the only Big Bad to successfully kill someone onscreen.
Slobs Versus Snobs: The relationship between the more materially-focused Southern and the more spiritually-focused Northern Watertribes seems to be like this. Turns out there's something more to it.
Upon learning that Korra was the Avatar, the Order of the White Lotus set up a large compound in the Southern Water Tribe for her to live in, to fulfill the promise they made to Aang to protect his reincarnation. There, Korra underwent her Avatar training, under constant watch from the Order. She was allowed to leave, but only with supervision and as long as she did not go outside the South Pole. When Tenzin tried to delay her Airbending training, and thus ultimately her freedom from the compound, Korra ended up running away in order to follow him to Republic City.
This is eventually revealed to have been set up because of Zaheer's previous attempt to kidnap Korra when she was a child. They were imprisoned because they got caught in the act.
For Korra's airbending training, Tenzin attempted to set up something similar on Air Temple Island. This fell apart remarkably fast.
The first humans that lived in the lion-turtle cities knew nothing about the others and only ventured out into the world for food. This changes after the spirits leave for their own world and the humans are free to spread out.
Small Steps Hero: Korra decides to risk unleashing 10,000 years of darkness on the world just to save the life of one girl.
Snowlems: Ikki suggests that Katara use waterbending to make snowmen chase the children for fun.
The pro-bending ring is far enough above the water below that you'd expect injuries, at least from the non-Waterbenders, but this trope is in full effect.
Waterbenders in pro-bending are the only ones allowed to hit their opponents in the head due to this trope.
In a nod to the previous series, when Korra jumps into the ocean from a great height, she bends the water up to herself to soften her landing.
So Last Season: In Book 2, the Dark Spirits are immune to normal bending, even Korra's Avatar State-enhanced bending. Bending can disperse them, but they reform quickly. Only Unalaq's spiritual waterbending has proven consistently effective when performed properly, and it doesn't actually stop them, just calm them down and get them to leave. They're non-corporeal energy beings corrupted by darkness, instead of regular flesh and blood.
And then this trope gets applied to the spirit-calming technique when it proves to be worse than useless against the vine infestation in Republic City.
The Equalists of Book One are group of non-bending revolutionaries led by the terrifying Amon. While they're quite dangerous (even having the backing of a major technology corporation), their influence only really extends to Republic City.
Chief Unalaq of the Northern Water Tribe in Book Two isn't personally quite as scary or as powerful as Amon, but he commands far greater resources (including a horde of bending-immune spirits) and his plans threaten the entire world. Additionally, he's serving a far greater evil: Vaatu, the spirit of chaos and darkness.
The Red Lotus of Book Three are exceptionally powerful anarchist benders with unique abilities (though nothing quite as broken as Amon's psychic bloodbending) who seek to eliminate all world leaders, but they have only four main members. Nevertheless, Zuko considers them capable of taking on the entire world, and they prove him right by assassinating the Earth Queen and successfully plunging the entire Earth Kingdom into chaos. It's also later revealed that the Red Lotus has plenty of mooks hidden across the entire world, with Unalaq once being one of them.
Spotlight-Stealing Squad: Mako and Bolin tended to overshadow Korra in previous seasons. For this reason, the writers let them have several moments in book 3 where they go off on their own while letting Asami be Korra's partner to maintain focus on Korra.
Spinoff Sendoff: The first episode features an appearance by an elderly Katara as one of Korra's trainers. She encourages Korra in her plan to run off to Republic City, helping set the series in motion.
Toph's daughter Lin Beifong is the captain of the police metalbenders in Republic City. In Season 3 we meet her other daughter (to another father) Suyin, who is just as stubborn and strong-willed as Toph and Lin. We also get to see Suyin's kids: Baatar Jr, Opal, Huan, Wei and Wing.
Aang and Katara's son Tenzin, who is teaching Korra to airbend just as Roku's descendant Zuko taught Aang to firebend. Tenzin also has two other siblings, Kya and Bumi, named for characters in the first series. Tenzin himself brings his wife Pema, and four children, Jinora, Ikki, Meelo, and his new born son Rohan .
Zuko's grandson, General Iroh of the United Republic military forces, appears in the final arc to assist in the fight against Amon. Iroh, unlike other examples, actually has the exact same voice as his Grandfather.
Earth King Kuei's daughter appears in Book 3. Sadly, while her father was The Good King, she is a complete Jerkass evil tyrant and one of the villains.
Staged Populist Uprising: Amon, who claims he was gifted by the spirits to cleanse the world of all benders, is himself a Waterbender.
Standing Between The Enemies: Avatar Wan tried doing this between his old human friends who left the lion-turtle city and now were living in the wilds but not in harmony with nature, and his spirit friends who were furious at the humans for burning parts of the forest. Unfortunately, their minds were clouded by hate and when Vaatu arrived and empowered the spirits hatred, not even Wan bonding with Raava for a short time could quell their anger. He passed out and woke up, learning all humans were killed in the battle.
At first glance, Wan Shi Tong's "little men in boxes" line sounds like a silly thing you'd hear in The Roaring Twenties or so. But remember who gave him that information: A bunch of foxes.
Zaheer spends most of the third season quoting a airbending master about achieving weightlessness and flight. In the finale, he is defeated when Korra wraps a chain around his leg and slams him into the ground, or in other words is quite literally dragged down to earth.
Stereotype Reaction Gag: In "A Leaf in the Wind" Korra Downplays and Invokes this when she asks Bolin to teach her some pro-bending moves. He agrees but isn't sure how his earthbending will translate to her waterbending. She responds that she can earthbend, and Bolin freezes up before Digging Himself Deeper, stumbling through an apology about making assumptions based on her Water Tribe clothes. After letting him squirm a little, she allows that he was right, she is a waterbender, and a firebender, too. Bolin's brother, who saw her as just a common fangirl up to that point, does the math:
Mako: You're the Avatar, and I'm an idiot.
Storybreaker Power: Ghazan's lavabending is this. He can turn any rock into lava, which can only be blocked by an earthbender, whose rocks Ghazan can turn into more lava. It's rather telling that he is ultimately defeated when Bolin unlocks lavabending too, and Bolin still needs Mako's help to actually gain the upper hand on Ghazan. Even then, Ghazan ultimately kills himself instead of losing the fight.
Stylistic Suck: The Nuktuk, Hero of the South film presented in Night of a Thousand Stars is this trope... for the first half, at least.
Sudden Name Change: The "penguins" seen way back in the first episode of ATLA had their name changed to "penguin-otters".
Tonraq and the rebels' attempted assault on the harbor city became this when the Dark Spirits were found to be fighting alongside the Northern Water Tribe.
When President Raiko finds out that Unalaq will release Vaatu and their army of Dark Spirits will destroy the world, he refuses to mobilize his troops, because assaulting the South Pole would be suicide under these conditions.
Super Empowering: Lion turtles used to do this with humans via energybending, granting them the various bending powers.
Supernatural Martial Arts: Just as technology has advanced, so have the bending arts, with many hybridized styles shown even in just the first chapter in addition to the more classic bending styles. Mako and Bolin's styles show shades of modern boxing and kickboxing, despite wielding separate elements.
Suspiciously Similar Substitute: Unalaq to Tarrloq. Both are charismatic politicians who are also powerful waterbenders whom Korra allies herself with early on. They both also have a Secret Art that we've never seen in action before. They also both then seem to turn out to be a Well-Intentioned Extremist who is trying to use the Avatar to his own means.
Aang's children are a male Airbender who feels the weight of the world on him, a female Waterbender who tries to play peacemaker, and a male nonbender who has a lot to prove compared to the others. Where have we seen that dynamic before?
And then Tenzin's own children are also a stubborn boy, a mostly-sweet girl, and the one caught in the middle, so the pattern's shaping up to extend to a third generation, more or less.
Take Our Word for It: No one ever explains just what Vaatu's "ten thousand years of darkness" actually entails. All that can be known is that humans will be annihilated, and Vaatu will reshape the world in his name.
Tall Poppy Syndrome: Benders believe that they are tall poppies that envious Equalists want to cut down.
Teens Are Short: Averted. Korra is as tall as most other adult women, Mako is very tall indeed, Bolin is still within a reasonable adult height even though he's shorter than his brother, and Asami is slightly taller than Bolin. It's part of the Art Evolution from the original series, which played this trope straight.
Jinora and Korra's varying execution of airbender footwork highlights their temperments. The more showy Korra navigates airbending training gates with lots of energetic spinning. In comparison, Jinora's approach to the course is fairly clinical: she turns on a dime but keeps her upper body rigid.
The same goes for spirit healing: Unalaq's technique has a lot more rapid, circular motions to the point where it looks flamboyant, whereas Korra's is more controlled and firm, perhaps inspired by her airbending training.
In-universe, Tarrlok identifies Amon as his brother Noatak, despite Amon's appearance being concealed, by the distinctive feel of his bloodbending.
In "And the Winner Is...", the Wolfbats, having just cheated their way to victory, ask if anyone else wants to take them on. Amon answers the call.
In "When Extremes Meet", Korra taunts Tarrlok about having no water to bend after destroying his office (which had a wall fountain). Unfortunately, she forgot about another source of water nearby.
The Missus and the Ex: Mako has this reaction when with Korra and Asami at the same time due to his on/off relationship with both of them. There is a hilariously awkward moment in the first episode of the third season where he addresses both of them formally as if speaking to a superior officer because he just does not know how to relate to the two of them together. Does not help that the two women are good friends.
Tenzin as well, when Lin Beifong and his wife Pema are shown together.
There Was a Door: Korra's Establishing Character Moment has her Earthbend the wall of her room to make an entrance. Her parents probably did not have that in mind when they wanted her to come meet the White Lotus members sent to verify her Avatar status.
Thou Shalt Not Kill: A notable aversion. Even heroic characters (especially Korra) sometimes threaten or aim to kill when they're extremely angry. Mako and Suyin have even done it, albeit in the heat of battle.
Throw the Dog a Bone: Cabbage Merchant, The Chew Toy and Recurring Extra of the original series, earned enough of a fortune during the peace times that he was able to found a technology company in Republic City. However, it's implied he or at least his successors are dirt cheap, because a lot of the company's product line is cheap knock-offs of Future Industries products.
Throw It In: In-Universe: Bolin (as Nuktuk) plants a kiss on Ginger, saying "it felt so right". Ginger is horrified, but Varrick likes it so much that he keeps the kiss in the film.
Book Three starts two week after the end of the previous season, and the denouement skips ahead a couple weeks, allowing the characters to recover (to an extent) from the injuries they sustained during the final battle.
Book Four is set three years ahead, with some flashbacks to fill in the gap.
Title Drop: The first three chapter names are mentioned by a character.
"Welcome to Republic City" is Gommu's cheery dialogue on realizing Korra is a Naďve Newcomer.
Tenzin tells Korra the key of the airbending device is to be like "A Leaf in the Wind".
People are lured to Amon's rally to learn about "The Revelation".
To Hell and Back: In a way. Tenzin enters the spirit world to find his daughter, and enters the Fog of Lost Souls, which inflicts insanity on anyone caught in it, overcomes its effects and takes is daughter and his siblings out.
In "The Voice in the Night" while at Tarrlok's gala, Tenzin has to chase after his son Meelo, who has apparently decided that something offscreen is a toilet.
In "When Extremes Meet," Team Avatar joins hands and vows to stand by one another through whatever comes...and Meelo floats down onto their joined hands by using a fart to air bend.
In "Turning The Tides", Meelo is given to Lin to look after, who promptly tells her he needs to poo... and starts grunting. Lin understandably holds him with her metal cables at arm's length. Meelo also likes to airbend his farts as part of his combat style against the Equalists.
Meelo is very good at this trope.
Varrick dropping money out of a stuffed Platypus Bear's anus twice in "Civil Wars Part 2". Bonus points for one random guy shouting "That platypus bear is pooping money!" and the farting sound effects to top off the joke.
Tonight Someone Kisses: In perfect Avatar tradition, it was used as a teaser for "Spirit of Competition." The clincher? This happened the day before April Fool's.
The menu screen on the DVDs has clips that give away key plot points.
The trailer for Book 4 spoils Korra's meeting with Toph
Traumatic Superpower Awakening: Traumatic might be a bit much, but Zaheer unlocks an advanced airbending technique when P'Li is killed, which severs his last earthly tether, enabling flight.
The Triads and the Tongs: The Triple Threat Triad, a pan-elemental bender organization that collects protection money from shopkeepers, and its referenced competitors, the Red Monsoons and the Agni Kais.
The waterbender from the Triple Threat Triad after Korra taunts him.
Korra when Tenzin cuts off the radio seconds before the pro-bending match being played is finished.
Tenzin displays this on hearing that Korra is participating in a pro-bending match.
Tahno gets one after Korra beats him in the tiebreaker.
Two-Part Trilogy: Books 2, 3 and 4 form one. While Book 1 is more of a self-contained miniseries that doesn't effect Book 2 in any significant way, Book 2, while having a standalone plot, has a stronger effect on Book 3, which is inter-linked with Book 4 in dealing with the conflict with the Red Lotus Society as the world undergoes great changes.
Undercover as Lovers: In "The Revelation" Korra grabs Mako's arm and leans in to provide a more convincing cover when they approach the bouncer at an Equalist rally.
Underdogs Never Lose: The Fire Ferrets were considered the underdogs going into the tournament. Subverted as the Wolf Bats win through illegal moves. Then gets double-subverted as the Wolf Bats did not get away with their victory, and they paid the price
Understatement: In the finale, Desna describes his father as a "deplorable man." He usurped the throne of the Northern Water Tribe by getting his brother exiled, invaded the South, created dark spirits, intentionally fused with an Eldritch Abomination, and tried to destroy the world, starting with Republic City. "Deplorable" might not be a strong enough word.
Unalaq also left an injured Desna to die after Desna's efforts to help open the Spirit Portals fell. Sure, Unalaq is "deplorable".
Unexpected Character: Iroh and Zhao's appearances in the Spirit World were unexpected to say the least, with no previous mention of them beforehand.
Unflinching Faith In The Brakes: In the finale, Bolin is being attacked by mecha-tanks, which Naga unexpectedly stops by grabbing their grappling hooks and tugging. The mechas tumble over and stop just shy of Bolin, who never moves. Then he says "Whoa!"
Unflinching Walk: While pursuing Amon onto an Equalist zeppelin, Korra uses firebending to cause a large explosion. His mooks are knocked aside, but Amon casually boards.
Firebending's advanced technique of lightningbending, once only demonstrated by Azula, Iroh, and Ozai, is, after seventy years and an industrial revolution, mundane enough that firebender menial laborers use it to run the power plants. It is also noted that firebenders who are strong enough to use this gift are not common, though.
Metalbending, once Toph's unique innovation, while still fairly difficult to learn. She decides to teach it at a school and it is now practiced by an entire police squad.
Combustion Man's explosion-based combustion bending is still quite rare, allowing P'Li to remain a serious threat in Book 3, but the particulars of how it is performed are well-known, as are its weaknesses.
Asami is able to pilot a Mini-Mecha because its controls are similar to a Future Industries forklift.
General Iroh can pilot a airplane, to an extent, despite only becoming aware that they exist the day before.
The Unfavorite: Kya and Bumi according to their recollection that their father, Aang took Tenzin on vacation with him, leaving them behind.
Ungrateful Bastard: President Raiko expels Korra from Republic City after she had enough of being scapegoated by him and told him the spirits and the vines would stay until she figured out how to remove them without making the spirits angry. Also the Republic City Press who berate her despite her best efforts. Note, Korra's saved all their asses from Amon and Vaatu, yet no one in the city except for her friends step up to her defense.
Unskilled, but Strong: The first benders had no actual skill; they were given an element by their lion-turtle when they left the city, and gave it back when they returned. They never had a chance to train. Wan was the first to learn how to truly use his element, becoming the first real firebender after training with a dragon.
Hunter: The way Wan uses fire...I've never seen anything like it. It was like it was an extension of his own body.
In "The Revelation," Korra and Mako do battle with Equalist chi-blockers who are riding motorcyles.
In "When Extremes Meet," Team Avatar uses Asami's satomobile to attack, and defeat, Equalist forces staging a jail break. At one point it becomes a car vs. motorcyle battle.
Victory By Endurance: The Fire Ferrets win two matches by simply dodging or blocking their opponents' attacks until they've tired themselves out, at which point the Ferrets win with ease. Mako impressively manages this when it's three-on-one.
Villain Has a Point: The first three Big Bads each had a point, which is actually discussed in Book 4. Their problem was that they were imbalanced in their belief.
Amon was all about promoting equality, but did so in a violent manner.
Unalaq felt it was wrong to lock away the spirits, but was ready to wipe out humanity for it.
Zaheer encouraged freedom, but did so suddenly, which made people go crazy.
Villain Ball: Unalaq's plans might have succeeded if only he hadn't been so heavy-handed and petty in his execution. He takes the time to ruin his brother's life, even though this gains him nothing and alienates Korra, who he still needs to complete his plan. He also completely takes over the south, which also didn't win him any points with Korra. He could have gotten Korra to open both portals and she would be none the wiser to his plan, right up until it was too late, if only he had shown a little restraint. Even if he absolutely had to secure the portal to make sure no one found Vaatu, he could have just secured the portal and nothing else, which probably would have worked if he made up a half-decent excuse.
Villainous Rescue: When Tarrlok is about to flee the city with Korra as his hostage, Amon shows up and de-bends him, but he came to kidnap Korra too.
Villain World: This was what Vaatu and Unalaq wanted to create: A world where spirits rule over humans. They almost succeed.
The main setting of Book 3 is this. The Earth Kingdom is ruled by a tyrannical Queen, who extorts her own citizens, has the Dai Li proscribe her own people, especially Airbending children, and sends poachers to hunt down endangered animals, including Sky Bison, which are considered sacred animals to the near-extinct Air Nomads. The Earth Queen is dead, but now the Earth Kingdom has fallen to anarchy and chaos, which is exactly what the Red Lotus wanted.
The Voiceless: Ginger, to begin with. It comes as a genuine shock when she actually talks for the first time.
Voodoo Shark: The somewhat infamous and inexplicable "Jinora ex Machina" in the season two finale was partially explained in season three with the introduction of spiritual projection, which Jinora says is an advanced airbending technique "with a bit of spirituality", with a Hand Wave that Harmonic Convergence amped up her ability to do it. However, this begs the question of what projecting your spirit the way Jinora does even has to do with air or airbending at all.
Walking the Earth: Korra at the start of Book 4 and its later revealed that Toph is currently doing this.
Wardrobe Flaw Of Characterization: Mako wears an old scarf at all times, even when dressing to the nines for a fancy date, because it's one of the few mementos he has of his parents. Something of an Informed Flaw; although some characters react to it as though it clashes horribly with his fine clothes, to the audience it looks perfectly normal, even stylish.
Welcome to the Big City: The plot of the first chapter, as sheltered Country Mouse Korra realizes Republic City isn't the shining beacon of harmony and prosperity she thought it was.
Well-Intentioned Extremist: The first three Big Bads each championed a cause that was a legitimate concern, but in each case they went overboard in trying to correct for it, ultimately ending up going to the opposite extreme.
Combined with Wham Shot, from "A New Spiritual Age". Not so much the line, but who is saying it.
Iroh: You two look lost. Maybe I can help.
And then we have this gem from "Darkness Falls".
Zhao: I am Zhao the Conqueror. I am the Moonslayer! I will capture the Avatar!
"The Metal Clan".
Korra: "Why didn't you tell me you had a sister?"
Lin: (tersely) "Half-sister."
From the season fourth's trailer: "THREE YEARS LATER". Also:
Korra: "I can't believe it...Toph?"
From "Korra Alone", when faced with a vision of herself in the Avatar State for the second time:
(the dog starts growling, facing the apparition)
Korra: "Wait... you can see it too?"
Wham Shot: Easily missed if you weren't paying attention or didn't know some of the mythology of the show from the first series. The first time Tarrlok bloodbends Korra and kidnaps her, the "camera" pans up to the night sky showing that there was a crescent moon, but not a full moon. Based on prior mythology, this is Beyond the Impossible.
The first episode of Book 3 starts with Bumi airbending for the first time.
In "Original Airbenders", Kai and Jinora are suddenly captured by what seems to be a normal group of thugs. However, their leader is wearing an Air-bison fur cape.
What The Hell, Townspeople?: Despite Korra saving the city from Amon, the city and the entire world from Unalaq, Korra depressingly notes she has an 8% approval rating in Republic City. Then President Raiko kicks her out after she stopped a new Airbender from committing suicide without anyone stepping up to call him out on his bullshit.
When the Planets Align: Happens every ten thousand years, signifying a harmonic convergence event. The energies of the two spirit portals combine and allow either Raava (Order) or Vaatu (Chaos) to dominate the other. The loser is absorbed and slowly gains strength until the next convergence, and the cycle repeats.
With Great Power Comes Great Insanity: This was the reason why bloodbending was declared illegal and why Hama was evil in the first place—the continued use of bloodbending causes waterbenders to go insane and develop an insatiable hunger for power—which was the case with Yakone, Amon, and Tarrlok frequent use of bloodbending turned them into even bigger monsters than they started out.
World-Healing Wave: In Book 3, it's revealed that the Harmonic Convergence also restored the presence of airbending in the world, granting it to many people who before could not bend.
The World Is Always Doomed: It seems like the end of the Hundred Year War just doesn't cut it. Every season, the world is always under threat; Book 1 featured the Equalists who, while mostly confined in Republic City seek to expand their campaign to eliminate all bending across the world. Book 2's Big Bad Vaatu seeks to plunge the entire world in eternal darkness. Book 3's plot features Korra having to stop a cabal known as the Red Lotus, who seek to eliminate all the world's governments and bring it to complete anarchy.
Wretched Hive: Tenzin acknowledges that Republic City has gotten a lot worse since his father's death, to the point that he considers his responsibilities as a councilman more important than teaching Korra.
Amon claims that his ability to remove a person's bending is a gift bestowed upon him by the spirits, who have determined that the Avatar failed in its duties of bringing balance to the world. Amon is actually simply utilizing another form of Wrong Context Magic; by combining bloodbending with chi-blocking he is able to strip away a person's bending ability.
Sokka discusses this trope in a flashback. While bloodbending without a full moon appears to break the laws of bending, Sokka quite reasonably points out that the fact that nobody has ever done it before does not mean it is impossible, given other examples of Wrong Context Magic that he encountered in the original series and especially when all evidence indicates that it actually happened.
The Red Lotus in Book 3 all have abilities that don't fit into the normal rules of bending.
Wuxia: As with its predecessor, a heavy genre influence.
Xanatos Gambit: Amon makes a public demand over the radio that the city government shut down the Pro-bending Arena and cancel the championship match. If it works, he shows that he can make the government fold under pressure. If it doesn't, his original plan goes forward and he demonstrates his power regardless.
Varrick can come off as playing Xanatos Speed Chess all the time in his plans to get support for the South, take over Future Industries and make boat loads of money. Hell his introduction can be seen as this: either no one tells him he's not flying (and he knows that they're all yes-men in his pocket) or someone points out that he's not (and he gets his claws on someone who isn't afraid to be honest). If Asami didn't follow his advice to send tanks to the south (which he stole) it wouldn't have mattered because in a matter of weeks he'd be able to buy the company out right because it was in trouble, he just didn't want to risk competition for the bidding...
Yandere: Eska could give Yuno a fair match in that department.
You Are Not Alone: In chapter eight, when Korra is crying about not being able to take the burden of saving the city alone, Mako, Bolin, and Asami come along and remind her she is not alone and they are there to help her save the city.
You Are What You Hate: Amon is not only a waterbender, but a bloodbender, which makes all his talk about how benders only use their powers to gain an unnatural advantage over others deliciously ironic.
You Keep Using That Word: Technically the words "electrocute" and "electrocution" exclusively mean "to kill with electricity", though they long ago passed the point in common usage where it can mean non-fatal shock (shock, or electrify, being the "correct" terms in non-fatal electrical incidents).
You're Just Jealous: After Mako wrongly accuses Korra of using his brother for some Operation Jealousy ploy, she sees through his facade and remarks that he is jealous. This seems to be a favorite tactic of Mako since he uses the same argument against Korra when she insists that Hiroshi is an Equalist and Mako believes she is only doing this because she's jealous of Mako's and Asami's relationship.