Aborted Arc: Watching the first few episodes of Book 1, one gets the impression that the Triads are being set up for a much larger role than they ultimately end up serving: They are seemingly part of the reason Tenzin decides not to move to the South Pole to train Korra, and Skoochy informs Mako that the main three triads are hiring muscle for "something big", with Mako speculating that they are preparing for a turf war. Whatever the triads were planning is made irrelevant once Amon starts his revolution and is never explained or elaborated on even when they reappear the next season.
Absurdly Spacious Sewer: Republic City has a massive underground tunnel network, home to both the Equalists and the city's homeless population.
In "Turning the Tides," Tenzin sees the Equalists attacking Air Temple Island, where his pregnant wife and three kids are, and he's too far away to help.
In "A New Spiritual Age", Tenzin recaps about how he was hesitant to let Jinora go into the Spirit World alone with Korra. Jinora doesn't return from the Spirit World after a skirmish with Unalaq and the Dark Spirits.
Advice Backfire: After Bolin realizes that a continued relationship with Eska is undesirable, he goes to Mako for advice. Mako suggests just breaking it off immediately. Eska threatens to feed him to piranhasharks. Then he turns to Asami, who suggests he tell her the truth. Eska decides to solve the problem by forcing Bolin to marry her. Finally, he takes Varrick's advice, which is to run like hell. Eska's having none of that.
Pema's own advice to Korra on how to deal with her crush Mako doesn't exactly work out the way Korra hoped it would.
Related to the first thing above, Bolin gets into a deep relationship with Opal. Varrick trys giving him advice, but Bolin (after what happened last season) replies "Um...no."
After it's revealed that Varrick is a villain, it's shown that his friendly and eccentric personality isn't a facade. This makes it rather unnerving when he starts threatening Mako.
Zaheer is rather genial, even to his captors and enemies. However, he can be cold-hearted and unforgiving of any subordinate who compromises his agenda or proves to be a major liability, which is what he did to Aiwei.
Age Cut: In "Welcome to Republic City," four-year-old Korra affects an intense expression as she firebends directly into the camera, obscuring the scene with a burst of flame, which seventeen-year-old Korra disperses while wearing a matching expression.
By the end of the first season finale, even though both Tarrlok and Amon/Noatak did many horrible things, the revelations of their history and their tragic deaths ultimately made both of them feel like this even in spite of it.
Alice Allusion/Spot of Tea: When Korra enters the Spirit World, she encounters Iroh who takes her to a cottage where she has tea and cake with him and a group of daffy spirits. Korra is however informed that the cake won't make her gain or lose weight (or grow and shrink, as the case may be).
Amazon Chaser: The old seafood-seller in "Korra Alone" seems very impressed by Avatar Kyoshi's amazing feats of strength.
"Taking down a rhino-squid with one hand? Now that's the kind of lady I'd like to get to know!"
Amicable Exes: Mako and Asami after season one, and Mako and Korra after season two. And it looks like Eska and Bolin have also managed this.
Tenzin and Lin Bei Fong are a bit of a subversion- originally, they weren't Amicable Exes, with Lin jealous of Tenzin's now-wife. After a few years, though, it looks like they've managed to get over it.
Appeal to Force: Korra threatens to kill a judge twice, first in an attempt to get him to reduce a sentence from the death penalty, then to force him to annul the conviction entirely (ironically, after she'd asked Unalaq to give the accused rebels a fair trial). The judge was on the take anyway, but it's still a sign of her brute-force approach to solving problems.
Arc Number: The number ten thousand is heavily featured in the "Beginnings" two parters. Wan means ten thousand, and he lived about ten thousand years before Korra. The Harmonic Convergence, a battle between Raava and Vaatu, occurs every ten thousand years. Vaatu boasts that he lived ten thousand lifetimes before humans "crawled out of the mud".
This has some context. If you're familiar with Taoist philosophy, you'll know that the number ten thousand is used as a shorthand for anything that is too great or numerous to count. In particular, "the ten thousand things" is used to refer to everything that emerged from the duality of Yin and Yang, which is... well, everything.
Arc Words: "Light in the dark" in Book 2. The phrase, originally dropped casually by Unalaq in a seemingly metaphorical context, turns out to have quite a literal meaning of Raava being reborn out of Vaatu.
Are We There Yet?: In "Welcome to Republic City", the introduction of Tenzin and his family features his daughter Ikki asking this over, and over, and over...
Tenzin: [While son Meelo gums his head] Yes, Ikki. As I've been telling you for the last fifteen minutes, we are — finally — here.
Are You Pondering What I'm Pondering?: In "The Spirit of Competition," Bolin asks Mako what he thinks of the idea of asking Korra out. Mako responds that he likes her, but he's already in a relationship, prompting Bolin to clarify:
Bolin: I was talking about a girlfriend for me! Leave some ladies for the rest of us!
Armor-Piercing Question: Mako to Prince Wu after Kuvira usurps his position as ruler: "If you were an Earth Kingdom Citizen, do you think you're the kind of person you want as your king? What have you ever done for your people?"
In "Welcome to Republic City", Korra's readiness to fight gets her pegged as a Destructive Savior by the metalbender cops.
In chapter eight, "When Extremes Meet", Asami is arrested for trying to stop oppressive measures against non-benders. Tarrlok claims that her father's connection to the Equalists is the reason, and when Mako and Bolin try to come to her defense they are put in the slammer, too. Ultimately, Tarrlok admits directly to Korra that he is simply doing this to manipulate her and force her cooperation.
Art Evolution: Art director Bryan Konietzko has discussed his evolution towards more realistic proportions and less oversized heads. This is particularly noticeable when redrawn original series characters appear as stills during the Opening Narration. Far greater detail and more CGI is used, leading to a far cleaner and more realistic look than the original series. Book Two also includes minor detail improvements on most of the characters.
Zaheer is a villainous version, being very interested in Air Nomad culture but to a decidedly negative extreme. Then he got airbending.
New airbender Otaku, who was an Air Acolyte before he acquired the gift himself.
Asshole Victim: The Earth Queen was a tyrant who forcibly conscripted airbenders in preparation for a war against the United Republic, and dined on endangered species such as sky bison, but her death at the hands of Zaheer was particularly chilling.
Korra is an adorable teenage girl, but has been a very talented Avatar ever since she was four.
Tenzin's kids are very cute, yet much stronger than you'd expect them to be.
The best way to describe Bolin in two words would be "Badass Adorkable". He may be goofy, but don't underestimate him.
Post Time Skip, Opal definitely counts. She's just as adorable as she was three years ago, but much more badass and capable.
Badass Army: It takes more than a mere Avatar to impress Republic City's metalbending police force. The Equalist chi-blockers are also formidable foes, skilled in martial arts, ambush tactics, and motorbike-riding.
Book 3 gives us the airbenders who escape Ba Sing Se. They manage to evenly hold their own against the Dai Li (a group who gave protagonists of the original series a ton of trouble) despite being inexperienced.
Vaatu: [casually swats Wan away] I lived ten thousand lifetimes before the first of your kind crawled out of the mud. It was I who broke through the divide that separated the plane of spirits from the material world! To hate me is to give me breath. To fight me is to give me strength. Now prepare to face oblivion!
In the finale "Endgame", Amon compliments Mako striking him down briefly with lightning bending stating that it's the first time anyone has ever gotten the better of him. He says it's almost a shame to remove the bending of someone so talented. Almost.
In the finale of Book 3, "Venom of the Red Lotus", Ghazan compliments Bolin, who had showcased his newly-learned Lavabending, smirking as he realizes how he escaped the lava-filled air temple. His words: "Not bad, let's see what you've got!", with a genuine smile on his face, almost as if he enjoys the fight.
Balloon Belly: In "The Spirit of Competition" Pabu gets one after joining Bolin for a night of binging on noodles.
Batman Gambit: In "The Voice in the Night", Tarrlok arranges for a group of reporters to accost Korra at a party he is throwing in order to force her to join his anti-Equalist task force. When they accuse her of cowardice and abandoning her duty to the city, she responds by immediately joining the task force.
Be Careful What You Wish For: A meta-example. The Mako/Korra romance largely originated from fans wishing Katara and Zuko were a couple. As it turns out, the relationship doesn't work.
Beam-O-War: Happens between Dark Avatar!Unalaq and Korra's Spirit Projection in the last chapter of book 2
In "Welcome to Republic City," Korra uses an Effortless Amazonian Lift to pick up Tenzin and his children to give them a group hug.
In "The Spirit of Competition" Mako unceremoniously grants his brother one in cheer when Korra pulls off an incredible "hat trick" single-handedly (much the same way he did in his introduction), and wins the match that gets them to the finals.
In Korra's fight with Tarrlok, his icicle-rain move results in several visible cuts, and she spends the next episode covered in the same cuts and multiple bruises.
At the end of Book 3, Korra looks terrible as she recovers from her fight with Zaheer. She has bags under her eyes and looks rather sallow. The President of Republic City even comments that she doesn't look so good.
Beleaguered Assistant: Zhu Li, Varrick's assistant. So much so that she hides in the stuffed platypus-bear with Varrick.
Belligerent Sexual Tension: Korra and Mako butt heads when they meet in "A Leaf in the Wind" and while infiltrating "The Revelation", but recognize that they have feelings for each other, and overtly act upon them once in "The Spirit of Competition".
Book Two has a Big Bad Duumvirate between Unalaq and Vaatu. Unalaq is technically Vaatu's herald, and while the latter was more powerful of the two, they, in practice share an equal amount of plot importance.
Book Three has a cabal known as the Red Lotus, the strongest benders in the world, with their leader Zaheer being a villainous airbender.
Big Fun: Iroh returns, even more calm and cheerful than he was in the original series, and having regained all the weight he lost.
When Bumi is introduced in the series, he's actually fit, however after his retirement from the Army the weight gained became notorious.
Bigger Bad: It was revealed that Vaatu, the spirit of darkness and chaos, is this for the series as well as to Unalaq. He takes on the Big Bad role in Book 2.. However, there were others that came after him, though are lower down the chain:
In Book 1, there's Yakone, an evil mob boss defeated by Aang decades prior to the story. The plot is set in motion by his desire for revenge, but he's long dead by the start of the series and even if he wasn't, he probably wouldn't have a direct say in what happened. The main villains (Amon and Tarrlok) are his abused sons who rebelled against him and tried to be good people in spite of him. It didn't work out.
Book 3 has Xai Bau, the original founder of the Red Lotus, a secret global organisation of which Zaheer and co are merely the most active members.
Big Good: Three characters qualify for the position: Raava, because she is the spirit of light and order and as such, the one the Avatars got their powers from to begin with; Korra herself, because she, as the Avatar, holds the power of Raava and is the protector of balance between mankind and spirits; and Tonraq, who is the leader of the Water Tribe Rebels in Book 2.
The Book Three finale has the Red Lotus defeated, the new Air Nation intact and stronger than ever, and Jinora earn her arrow tattoos. But the Earth Kingdom is still in chaos in the wake of Hou-Ting's death, the Red Lotus are revealed to have numberless agents hiding and plotting their next move, and the ordeal has left Korra physically and emotionally broken. She's confined to a wheelchair (and has been for a couple weeks), barely reacts to anything around her, and wears an expression of utter despair. The final scene has her shed a single tear at Jinora's ceremony, right before the credits roll.
The two-part mini arc "The Beginning" ends on a bittersweet note. Wan seals Vaatu away, but has lost all of his mortal friends in the chaos. As he is about to seal the spirit world away, he says goodbye to his spirit friends as well. He then spends the next few decades trying to bring balance to the world. For all his efforts, he dies on an unnamed battlefield, clad in broken armor lamenting how one lifetime just wasn't enough. The only comforting thought was that Raava vowed to stay with Wan through all his lifetimes, starting the Avatar reincarnation cycle.
When Tarrlok, Noatak, and Yakone bloodbend, their victims end up getting twisted into painful shapes.
Spirit possession in general - the experience is described as both this and Mind Rape, and leaves the victim as a Baleful Polymorph at best, and dead at worst.
Unalaq fusing with Vaatu. He turns into a Kaiju and starts sprouting tentacles.
Korra being poisoned by mercury. She remains completely conscious while feeling her body shut down, and even endures nightmarish hallucinations.
For that matter, Korra's hallucinations. Zaheer's face crumbles off to reveal Amon's mask underneath, Ghazan's neck twists around as he morphs into Unalaq, and Ming Hua's spine contorts horribly as her hair turns into Vaatu's tentacles.
Boobs of Steel: Korra is one of the bustiest girls in the show (if not the avatarverse), including the ones who are pregnant. She is also, needless to say, exceedingly powerful physically and bending-wise.
The first season begins and ends at the South Pole.
Tahno's first and last scenes involve him deliberately mispronouncing the word "Avatar".
Korra's first and final encounters with Amon are pretty similar. Both times, she and Mako infiltrate a massive Equalist rally where Amon attempts to debend several people execution-style. They also both end with Korra saving Mako's life and Korra revealing something about Amon to Republic City.
"A New Spiritual Age" begins in the night with Tenzin fretting to Bumi and Kya about Jinora's safety in the Spirit World, before his siblings go to sleep and he takes guard duty. Bumi tells Tenzin to wake them up if something bad happens. At the end, it's daytime and Korra wakes up with a gasp, waking the trio (Tenzin fell asleep during guard duty) and then Tenzin notices that Jinora's not waking up...
Bound and Gagged: Bolin and a few Triple Threat Triad members in Chapter 3. Then again with Korra after Tarrlok defeats her with bloodbending in Chapter 8. Tarrlok forgot the "gagged" part, though, and nearly got his face burned off by a livid fire-breathing Korra for it.
And again in Book 3 Chapter 9. Korra returns from the spirit world to find she and Asami have been captured by the Earth Queen's forces. Korra's straitjacketed, muzzled, and strapped to a gurney, Hannibal Lecter-style. Asami's cuffed to the wall.
Boxing Battler: Pro benders' fighting styles tend to be closer to simpler, more direct moves like a boxer's. This is most apparent in the 1-v-1 sudden death matches at close range, that has handwork based heavily on boxing.
And the difference in style really shows through when the quicker, less telegraphic style lets Mako and Bolin easily deal with the more tradtional techniques of the Dai Li.
Brand X: The Pro Bending tournament is sponsored in part by Flamey-O's Instant Noodles
Bratty Teenage Daughter: Discussed in "A Leaf in the Wind" when Tenzin expresses frustration with Korra, now his live-in student. After his daughters witness a particularly bad bout where Korra insults Tenzin's teaching skills, Tenzin tries to avoid the inevitable.
Breather Episode: After two pretty dark and brutal episodes, "The Spirit of Competition" is a fairly lighthearted story involving the pro-bending tournament and the show's Love Triangle, and comes right before a slew of Wham Chapters.
Breaking the Fellowship: Of a sort. While Team Avatar seems to be going strong by Book Two, the Fire Ferrets are not. Korra and Mako have left the team for unknown reasons, leaving Bolin as the sole original member. Team Avatar went back and forth with this trope in Book 2, which Bolin lampshades. By Book 3, they're back in action.
Break the Haughty: Korra was so used to being a natural prodigy at the physical side of being the Avatar that she assumed that connecting with the spiritual side was another game to win. This only changed when she admitted that the loss of her bending broke her heart.
Bridal Carry: After Naga arrives in Republic City with an injured Korra Mako shoos everyone away and carries her like this to Oogi. All the while he tells her how worried he was and assuring her that she's safe now. The implications of this are not lost on Asami.
After the Wolf-Bats' semifinal match, which the Wolf-Bats win the match in record time, the opposing team is carried away on stretchers, and one of them has a hole through his helmet.
In "The Aftermath", while fighting Mecha-Tanks made out of metal-bending-proof platinum, Chief Beifong resorts to the strategy of bending her metal bracer into a Blade Below the Shoulder, leaping up to the shoulders of one of the Mecha-Tanks, and driving the claw straight through the more vulnerable cockpit canopy. The chi-blocker piloting it is shown desperately dodging. After a few cuts, we see the Mecha-Tank as immobile, Beifong having bashed though most of the canopy segments.
Very frequent whenever Varrick is in a room, uttered either by him or someone connected to him - from his own Catch Phrase ("Zhu Li, do the thing!") to the Show Within a Show he directs. ("He's the biggest, baddest, bendingest man I know!")
Even Tenzin gets in on the act.
"Is it too late for you to un-retire?"
Korra also has this line in "Skeletons In The Closet": "I hate this being patient stuff!"
Bullying a Dragon: Being the Avatar hasn't stopped people from being overtly confrontational with Korra. Tahno does this intentionally, because Korra attacking him would disqualify the Fire Ferrets from competing against his team. Tarrlok also mocks Korra as a "half-baked Avatar in training" since she hasn't mastered airbending, despite the fact that she has mastered the other three. His bloodbending did allow him to best her in a battle, but it was a trump card he only played in desperation. He got a solid ass-kicking when he tried to beat her in a straight fight.
Burping Contest: In "The Spirit of Competition" Korra and Bolin get into one on their date, much to the horror of the other patrons in the restaurant. Korra seems to come out on top.
Varrick, the mogul who wants to market moving pictures, plans to call them "movers."
Call Back: In The Fire Lord and the Avatar, Toph briefly wonders if friendships can transcend lifetimes. When she meets Korra in Season 4, Toph calls her "Twinkletoes", her affectionate nickname for Aang, and remarks how it's been a long time since they last met.
One of the Fire Sages in "Beginnings, Part 1" (not the elderly Shaman) is voiced by tennis player Serena Williams. Previously, Williams had a role in the original Avatar: The Last Airbender playing a prison guard in the episode "The Day of Black Sun, Part 1: The Invasion".
Kuvira, a dancer and guard from Zaofu, is voiced by Zelda Williams. She has spoken in only a couple of episodes, "The Terror Within" and "Enter the Void". Turns out to be an Early-Bird Cameo, as she's the primary antagonist of Book 4.
In "The Voice in the Night". When Korra challenges Amon to a duel, he has his men restrain her and explains that while he could take her bending away, he will not because that would make her a martyr. Instead, he details a plan to take care of her last.
In Endgame, Amon ditches that plan and de-bends her anyway, before the revolution has spread beyond Republic City, when she saves the last airbenders and attempts to expose him as a bloodbender.
In "Peacekeepers," Unalaq reveals that he lied in the previous episode when he told Korra he didn't need her to open the Northern Spirit Portal. He only said that to prevent Korra from going after her father. Ergo, he has to clarify to an overeager Eska, commanded to capture Korra, that he needs the Avatar alive.
Car Fu: Asami crashes her car into an Equalist mecha in "Turning the Tides."
Casual Danger Dialogue: Chapter 6, "And the Winner Is" - The Pro Bending commentator Shiro Shinobi. He retains the same energetic and fast-paced reporting tone when the match concludes and the Equalists start emerging from the audience and using electric gloves to attack the event. He does not even change tone when they attack him, adding that he is peeing his pants without the tiniest vocal quiver.
Catapult Nightmare: Korra gets one in "The Voice in the Night", as a result of being truly afraid for the first time in her life.
Catfight: Subverted in "After All These Years" and "Korra Alone", Korra fights in an all-female underground Earthbending ring. The fight is not even remotely sexualised, in fact it's brutal and she walks away with actual, non-comedic injuries.
Attaining balance, whether it be in an individual, a city, or the world.
Recognizing one's own strengths and weaknesses, and by doing so, adapting to your personal environment and situation.
Though it became more prominent in Books 3 and 4, the series asks the overall question "Does the world need the Avatar anymore?"
Cerebus Syndrome: While the series is not lacking in the characteristic humor/wacky characters that TLA possessed, the overall tone is much more melancholic than the earlier episodes of TLA and is more on par with its darker episodes.
This trope is in full effect since Book 3, with the series taking bold moves that show things that are usually not reminiscent of a children's show. The biggest examples include: Zaheer sucking the air out of the Earth Queen being shown directly, P'li having her head exploded by her own bending, Korra's hallucinations after being affected by the poison, and her being depressed, wheelchair-bound, and with dark circles indicative of mercury poisoning after the finale.
Chair Reveal: In "The Sting" Mako rushes to Asami's office to tell her he knows who set them up and stole all her merchandise. The chair in front of her desk swivels to reveal Varrick, whom Mako thinks is behind it, smirking evilly, while Asami is overjoyed that he just "saved" Future Industries by buying a controlling interest in it.
Changing of the Guard: Korra and her compatriots take up the mission of their fore-bearers: to preserve peace and balance in the world.
At the end of the very first chapter, a blueprint of a Mini-Mecha can be seen on the wall of the Equalist base. Cut to chapter seven where they are wreaking havoc on the Metalbender Corps.
Asami grew up at her father's factory, not only learning to drive cars but other vehichles. Knowing how to work the forklifts allows her to drive the Mini-Mecha her dad built.
A recurring short term gun is when the 'camera' makes sure to get some flowing water or a pool in a shot, because a waterbender is going to be using it in a few seconds.
Wan's teapot returns in the Spirit World...
Chekhov's Gunman: ... to help Iroh to teach Korra an important lesson about spirituality and the nature of light and dark.
Chekhov's News: In "A Leaf in the Wind", Korra hears of up-and-coming pro-bending team the Fire Ferrets, and their star player Mako, via a live radio broadcast. Combined with Chekhov's Gunman in "A Leaf in the Wind," when Korra is reading the newspaper, and a picture of Tahno can be seen on the back of the paper. He shows up three episodes later as her rival.
Chekhov's Gunman: Gommu, the homeless guy from the first chapter who was really jazzed about that bush. Cut to the Book One finale and we find out why: the bush hides a secret passage to an underground city of homeless people (which just so happens to be composed of benders and non-benders who live happily side-by-side) where Korra & Co. hide during the Equalist occupation.
A bigger example of this would be Kuvira, who makes several small appearances as a random Zaofu soilder throughout book 3 and later turns out to be an antagonist in Book 4
Chekhov's Skill: In "A Leaf in the Wind", the spiral dodging movements and footwork Jinora demonstrates and Korra struggles to master later help Korra win her first pro-bending match.
At the racetrack in "The Aftermath" Asami mentioned she had taken self defense classes which later prove useful in subduing a chi blocker and her father
During Wan's training, Raava mentions that even if she or Vaatu were physically destroyed, they'd simply be reborn from within the other. After Unalaq, fused with Vaatu, destroys Raava, Korra rips Raava out from Vaatu and re-fuses with her.
During metalbending training in "The Terror Within", Bolin uses a tiny rock to land a pinpoint headshot on his opponent. He later uses this skill to nail P'Li in the head and momentarily disable her combustion bending, allowing Su and Lin to rescue Korra.
Su uses metalbending in a similar way in the finale, wrapping her own armour around P'li's head to block her combustion. Doing so turns the latter into a fine red paste.
When Korra teaches Opal airbending, the two circle around each other while manipulating a ring of wind. When the entire new Air Nation perform the same motion, it creates a tornado strong enough to pull Zaheer back to earth.
Season 1: The United Republic has one between the Council-led government forces and Amon's Equalists.
Season 2: The Water Tribe is fighting one, with Varrick's Southern Water Tribe rebels and Korra's uncle on opposite sides. It turns out said civil war was merely a pretext for the true threat—Vaatu's return for Harmonic Convergence.
Season 3: The Earth Kingdom is in a state of one after the Earth Queen's death, where citizens are fighting amongst themselves and remnants of the Earth Queen's government
Clear My Name: Korra hopes to clear her parents's names after they have been framed for an assassination attempt against Unalaq.
Close-Call Haircut: In "When Extremes Meet", Tarrlok's opening attack on Korra slices off a few hairs from her ponytail when she dodges it.
Unlike the original series, where with few exceptions anyone's Elemental Nation citizenship or Elemental Powers could be determined at a glance, the people of Republic City either use a wide range of colors in their fashion, or Downplay their traditional colors, as with multi-ethnic bender crime gangs the Triple Threat Triads. People that live in their countries of origin, and people who are deeply involved in their culture (like Tenzin and his followers, the Air Acolytes) still play this straight.
Mako and Bolin typically wear dark shades of gray in the fashion of Republic City, but they always have colored trim appropriate for their bending elements (russet for Mako, celadon for Bolin). Mako's sentimental scarf is conveniently red.
Pro-bending teams identify which element each team member bends by their color-coded belts and helmets.
Lampshaded by Varrick, who imported a red carpet from the Fire Nation because "they make the best red things!"
And in Book 2: Spirits, we have Dark Spirits who glow gold and normal Spirits who glow purple when "Spirit Bended".
Combat Commentator: Introduced in "A Leaf in the Wind," Shiro Shinobi, the announcer at pro-bending matches, narrates the action for spectators and radio listeners. He also narrates the Previously On segments, complete with footage edited to look grainy and sepia-toned.
He gets another moment in Book Two's "Night of a Thousand Stars", where, despite being in the audience at the time, he starts commenting on the fight between Varrick's Water Tribe mooks and Bolin. Granted, the fight was taking place in the pro-bending ring...
Combat Tentacles: The Metalbender Cops' weapons of choice are wrist-mounted retractable cables that can be manipulated through bending. They are used to tie up criminals and move around the city.
Vaatu uses these in battle with Avatar Wan and later Korra. And after Unalaq fuses with Vaatu to become the Dark Avatar, he uses these in his attack on Republic City and his final battle with Korra.
Season Three's Ming-Hua, when there's enough water around.
Conflict Killer: The first three episodes, and the pre-premiere commercials which contained footage from only the first two episodes, emphasized the criminal element of Republic City as the largest issue facing society and Korra's primary enemy. However, in "The Revelation" the Equalists, who had received only infrequent mentions and a single appearance of their leader, Amon, shifted the focus of the story to the bender/non-bender conflict after interrupting a planned gang war and eliminating the Triple Threat Triads in a single night.
In "The Revelation", Korra recalls the anti-bending protestor from "Welcome to Republic City" who gave her a hard time, and tracks him down so she and Mako can pump him for information on the chi-blockers.
When Korra explains to Tenzin that Amon can take away a bender's bending permanently, Tenzin mentions that previously only the Avatar had that power: This power was developed and used in the series finale of the original show.
In the flashbacks in "Out of the Past" we see Sokka speaking of both Combustion Man, and beating him with his boomerang, and Toph developing metalbending. The same chapter shows that even at aged 40, Toph still calls Aang Twinkle Toes.
During Wan's death scene in "Beginnings: Part 2," we see a burning battlefield with several Earthbender discs sticking up out of the ground. A similar battlefield can be seen along a road in "Zuko Alone."
In "The Stakeout" Zaheer eliminates Aiwei by throwing his spirit into the Fog of Lost Souls featured in Book 2.
Conspicuous CG: CGInote mostly provided by Moving Picture Company's parent firm Technicolor S.A. is used for many things, including Satomobiles, Aang's statue in Republic City, Yue Bay, the police zeppelins, the airbending training gates, the boat Korra travels on, and for a brief shot in chapter 7, Korra and Asami.
Lin Beifong, who is an Action Girl and is the chief of Republic City's Metal Bending Police, has a much deeper, and more commanding voice than the rest of the female cast by design to emphasize her position.
Conveniently Timed Attack From Behind: In "The Revelation" as bola-wielding chi-blockers advance toward a sprawled Mako and Korra, Naga frees herself. She and Pabu lunge bellowing (and squeaking) at them, at which they throw their smoke screen and flee.
Convection Schmonvection: Pops up rather gratuitously in Book 3. Ming-Hua's prison was in the heart of an active volcano, suspended at most a few hundred feet above the lava, but no one was any the worse for wear in that place. Additionally, Ghazan's lavabending is hot enough to instantly melt metal, but none of the Red Lotus are remotely phased by being close to it.
Cool Airship: The fully equipped Future Industries airship Asami provides Team Avatar in Book 3. It's larger and more luxurious than any other airship seen so far in the series.
Cool Bike: The Equalists' motorcycles and Asami's moped.
Cool Boat: Varrick has a whole fleet of cool ships and speedboats. He even has the first Battleship, named The Zhu-Li.
Cosplay: In the final match between The Wolf Bats and the Fire Ferrets, cosplayers of the respective teams can be seen in the stands.
The Corruption: In "A New Spiritual Age" it is revealed that spirits are affected by human emotion, and the darkness in human hearts can infect and distort the Spirit World and turn spirits into Dark Spirits, while positive emotions have positive effects. This is far more pronounced with the Avatar, since the Avatar represents Light.
Crapsack World: Prior to the start of the series, almost every leader in the world is either evil and/or a jerk. Tarrlok attempted to usurp leadership of Republic City, Unalaq got his brother banished and was working for Vaatu to plunge the world in eternal darkness, and the Earth Queen is an animal hating tyrant who has almost the entire Earth Kingdom as her domain and stole her people's freedom. It seems the only nation with a good ruler is ironically, the Fire Nation under Zuko's daughter, and the leader of the Southern Water Tribe is decent enough (even if he's a bit overprotective of his daughter).
Crazy-Prepared: The Satoplanes, despite being the first (and only) heavier than air flying machines in the world, have rear-firing bolas just in case they get into a dogfight.
Varrick built the prison with a special cell for himself because he had a feeling he'd end up there one day. He was right. On that note, Varrick, aside from having a hollow Platypus-Bear in his office aboard his boat (in case someone comes looking for him), prepares for crazy outcomes, like pet radio becoming a big thing
Creepy Twins: In season 2, Desna and Eska, the children of Chief Unalaq.
Crippling Overspecialization: The Equalist's mecha fighters were especially developed to counter Republic City's metalbending police, which they did very well...but a smart waterbender, like, oh, Korra, can get at the inner workings, and Bolin and Mako figure out effective fire and earthbending tricks to use against them too.
Cross-Popping Veins: In Chapter 7, when Bolin and Mako are swimming in Asami's pool, Bolin orders the Sato valet to dry him off, only for Bolin to immediately hop back in the pool. The valet understandably pops these.
"The Earth Queen" to the previous series episode "The Earth King". Both titles characters are sharp contrasts to each others.
"Korra Alone" to "Zuko Alone".
Cruella to Animals: Due to her allergies, the Earth Queen really hates animals...except when she's eating them. Rumor has it that she even ate her father's bear Bosco.
Crystal Spires and Togas: The city of Zaofu in season 3 is an Asiatic version of the trope. The citizens wear robes, but the spires are made out of steel rather than crystal, as the city was founded by Metalbenders. It seems to be a utopia that supports science, art and creativity in all forms and doesn't sacrifice natural beauty for its progress.
In "Welcome to Republic City," Korra's battle with the three Triple Threat Triad members is laughably one-sided, despite her numerical disadvantage.
In "The Revelation," Amon has absolutely no trouble dodging the captured bending criminals' attacks and closing the distance so that he can take away their bending. It's later implied that Amon was able to best so many powerful benders because he was using his bloodbending to slow them down and make their attacks miss.
In "The Revelation," Amon's lieutenant wipes the floor with Bolin and Mako, brutally so.
In "The Voice in the Night", Korra gets ambushed, restrained and broken by Amon in no time flat.
The Wolf-Bats score a first-round victory in "The Spirit of Competition", which was brutal enough to put the other team on stretchers. The very next chapter, the Wolf-Bats fall to a Curb-Stomp Battle against the Equalists and pay for it.
When Amon's Lieutenant attacks Asami after she has made clear what side she was on, she proceeds to knock his first rod out of his hand, and then uses his other rod to knock him out.
In "Out of the Past", Tarrlok is on the receiving end of this from Amon, who resists Tarrlok's bloodbending and de-bends him.
Amon's battle with his Lieutenant in "Endgame." The Lieutenant makes a dramatic speech and attacks Amon, who calmly bloodbends him into a wall before the Lieutenant even gets close enough to actually hit him.
At the start of Book 2, the Fire Ferrets are defeated faster than any other pro-bending team in history.
Cycle of Revenge: Aang debended Yakone, causing him to plot revenge by raising his children as Tykebombs. This, in turn, caused Amon to lash out at benders in general, and Tarrlok to become a corrupt councilman to succeed were his father failed. Tarrlok realizes this in the end and finally ends the cycle, and Yakone's legacy, by killing himself and Amon.
Also applies to Asami's family: Asami's mother was killed by the Agni Kai Triad, causing her father, Hiroshi Sato, to bankroll the Equalists and fulfill his revenge against all benders. Later on, Asami sees what a monster her father had become, which led her to retaliate and attempt to put her father down once and for all.
Damn You, Muscle Memory: In "A Leaf in the Wind", Korra accidentally earthbends when she becomes frustrated during her first pro-bending match, despite assuring Bolin just prior that she would only waterbend to stay within the rules.
Darker and Edgier: Korra is far darker than the original, which already had plenty of dark moments for a kids' show. According to the creators, they were surprised they could even get away with some parts of the show.
Book 1 has Amon's whole revolution, which among other things has benders lined up execution style as Amon methodically takes their bending away.
Book 3 has the Red Lotus. They earn their cred with interest when Zaheer uses airbending to suffocate the Earth Queen... onscreen. Then, the heroes stop following Thou Shall Not Kill in gruesome fashion, killing two of the four main villains personally and indirectly causing the death of one more.
Darkest Hour: There is one in Book 1 when Amon and his Equalists have taken over Republic City, and benders are having their bending taken away. Korra and her friends have to hide from the invasion, and the help they receive from General Iroh II goes haywire.
Book 2 is even more heartwrenching. Unalaq has managed to fuse with the ultimate dark spirit Vaatu, becoming a Dark Avatar, and he and Korra duke it out. But then...Vaatu pulls Raava out of Korra and brutally kills her, shattering Korra's connection with her past lives forever. As if that wasn't enough, Unalaq then grows to enormous size and starts wreaking havoc on Republic City.
Book 3 tops both 1 and 2 when Korra becomes incapacitated and wheelchair-bound after a poison (possibly mercury) nearly kills her. She is left traumatized physically and emotionally by the effects of the poison and feels she is not needed anymore. Now her job of keeping balance is now in the hands of the Air Nation and her other teammates while she's in convalescence.
In "A Leaf in the Wind", when Korra is trying to airbend, we zoom out to see that her target is actually a picture of Chief Beifong in the newspaper, which she then incinerates in frustration.
At the beginning of "And The Winner Is..." the Fire Ferrets are using photos of Tahno, the captain of the Wolf-Bats, as target practice.
Decade Dissonance: Very apparent with Republic City having all the technological marvels developed over the course of 70 years between the series, while many other locations look not so much different than at Aang's time (except more dilapidated).
After their leadership is beaten and Amon is exposed as a bloodbender, the Equalists lose their public support and are nowhere to be seen by the second season. Word of God is that there is a holdout, but they aren't a significant threat and won't appear in the show.
After Unalaq and Vaatu are beaten, the Dark Spirits vanish and the Northern Water Tribe soldiers retreat.
In "The Revelation" we learn that Bolin and Mako's parents were killed when Mako was eight by a firebender who was mugging them. Later in the same chapter, Amon claims that his family was killed, and his face scarred, by a firebender who extorted money from his non-bender family. Amon was in fact making up the entire story as part of his anti-bender propaganda. He was the son of former Republic City crime-lord Yakone.
In "Aftermath," we learn that Asami's mother was killed by a firebending triad member. This fact was used by Hiroshi Sato in order to tempt Asami to join the Equalists with him.
In "The Voice in the Night", Pema gives Tenzin quite a glare after he reluctantly allows Tarrlok to join them for dinner. He only acquiesces because according to Air Nomad philosophy, you cannot turn away a hungry guest. Ikki then trumps her mother when she really glares at Tarrlok after declaring him "weird;" her glare continues for twenty seconds, even after the camera pans away from her to cover his conversation with Korra.
In "Endgame", Bolin is on the receiving end of two glares after trying to reassure Korra by telling her that at least she is still able to airbend after losing the other three. He wisely shuts up immediately.
Death World: The world before the Avatar was infested by spirits hostile to humans, who were forced to take shelter on top of lion turtles for protection. Being banished into the Spirit Wilds is the equivalent to a death sentence.
Despair Event Horizon: When Tarrlok realizes that Amon is his brother, and that they have both become tools of their father's vengeance despite their best efforts, he abandons any hope to ruling Republic City and no longer even cares that he has had his bending removed. When Amon invites him to run away together, he instead kills them both.
Korra faces this herself after Unalaq and Vaatu "kill" Raava, breaking the avatar cycle and destroying Korra's connection to her past lives
And again in season 3, when she is left in a wheelchair after Zaheer's poison ravages her body. While everybody around her celebrates Jinora becoming an airbending master, Korra can only shed a single tear...
Destructive Savior: In "Welcome to Republic City" Korra ends up destroying more property than the gang members she caught when she first arrived in Republic City, which is quickly pointed out by the Metalbending Police when they try to arrest her. Chief Beifong is adamant that, Avatar or not, acts of vigilante destruction will not be tolerated.
In the Book 1 finale Amon is defeated, at the cost of Korra losing her bending and she is stuck in the worst crisis imaginable; the Avatar is no more. With Amon having blocked her connections to the three bendings (other than her newly-unlocked airbending), the Avatar is, for the first time in ten thousand years, non-existent. When Korra travels and sits by an ice cliff to reflect and cry over her loss of identity, she is visited by the spirit of Avatar Aang. One flash of Aang's energybending later, and not only does Korra have all three bendings back, but she also gives us a taste of her Avatar State.
Book 2 finale: Deus-ex-Jinora. Vaatu fuses with Unalaq and destroys Raava. Korra uses the Tree of Time to pull some super spirit mojo and goes after Unavaatu. So far so good. But it turns out she's not up to the task, and just as Unavaatu begins to use Unalaq's spirit-waterbending technique to corrupt her, Jinora's spirit suddenly appears from spirit aurora over Republic City with an orb of light and showers it on cosmic Korra and Unavaatu, which has the resulting effect of dispelling Unavaatu's spirit-waterbending corruption technique and then jumpstarting/revealing Raava's regrowth inside Vaatu, thus allowing Korra to free Raava and purify Unavaatu.
Book 3's plot is kicked off by the Harmonic Convergence turning several non-benders into airbenders, bringing the Air Nomads back from the brink of extinction after 170 years. However, many of those selected believe it ruined their lives, and it dips into Diabolus ex Machina when it empowers Zaheer, allowing him to escape imprisonment.
Towards the end of the Book 3 finale, Jinora's ability to somehow recognize the poison Zaheer used on Korra as metallic (Mercury evidently), as well as Suyin's ability to bend this liquid metal out of Korra when Metalbending is actually achieved by moving chunks of earth trapped inside solid metal, causing the metal to bend and warp into the desired shape, which would obviously be impossible for a liquid, even if we were to accept that solid bits of earth were somehow safely forced into and subsequently pulled out of Korra's bloodstream.
Diabolus ex Machina: Zaheer pulls this when he is able to use airbending to fly like Guru Laghima. It was the first time he had used it, and he wasn't even sure he could have pulled it off. But Laghima's teachings involve "losing your worldly desires"; and with P'Li's death, it's assumed as such that his last worldly desire was lost.
Didn't Think This Through: Tenzin and Korra at the start of Season 3. They want to rebuild the Air Nation with the new airbenders that have been popping up since the Harmonic Convergence, but fail to consider the ramifications of those airbenders not being born that way, but rather being granted airbending out of nowhere. As their first "recruit" bluntly puts it, he already has a life and family and has no intention of giving it all up to be a monk just so he can help revive a long dead culture.
Die or Fly: In "A Leaf in the Wind", when Korra is on the verge of losing the pro-bending match for the Ferrets, she suddenly gets how to move like a leaf in the wind.
At the end of the second season Tenzin, while looking for Jinora, is lost in a fog that drives a person mad with their greatest failures (Kya and Bumi have already gone mad and wandered off). He finally comes to terms with the fact that he is not Aang, and should not compare himself to his father and is able to overcome the effects of the fog.
Bumi discovers he can airbend when he's falling off a cliff.
Bolin first lavabends when Ghazan's lava is about to consume him, Tenzin, Asami, and Mako.
Diesel Punk: Despite the inspiration of Steam Punk, and use of aesthetics associated with it, the series fits squarely into this category; the internal combustion engine is in wide-spread use and the setting matches the 1920's, with all the cultural trappings.
Bolin: I'm sorry, no, no! I didn't mean to assume! It's that, I was just figuring... with your Water Tribe getup... that you are... a Water Tribe... gal.
Mako had been making increasingly snide and flippant remarks about Korra moments before and quickly realises how dumb a move this was.
Disappeared Dad: Aang was the "present physically, but absent emotionally" sort, enough that it is still a point of contention for Bumi and Kya decades later with regard to Tenzin remembering their childhood as idyllic and happy, while they do not. Part of it was Aang's sense of duty as the Avatar, but the rest was that Tenzin was an airbender, making Aang no longer the last that resulted in his playing favorites so dramatically.
Unalaq is also the "present physically, absent emotionally" sort. It was originally Played for Laughs that Desna and Eska are Creepy Twins who dress and talk alike and who finish each other's sentences. But Unalaq's hunger for power overshadows even his children. He orders them around like lackeys and ignores them when they come to harm.
Distress Ball: A minor one in "Turning The Tides," where Lin is defeated by the Lieutenant after attempting to grapple him with her metal cables. The three Airbender children come to her rescue and save the day.
Divine Conflict: In the two parter "Beginnings" we learn about the light and darkness spirits Raava and Vaatu and their conflict with each other. If either of them wins against the other on the day of harmonic convergence, there will be a 10,000 year age of light or darkness. The latter result, however results in The End of the World as We Know It, and there would be no coming back from that.
Donut Mess with a Cop: Lu and Gang are particularly fond of Varrick-cakes, a kind of snack cake with frosting and a jelly-filled centre.
Double Standard: Abuse, Female on Male: Played With in Bolin and Eska's relationship. On one hand, Eska's treatment of Bolin is emotionally abusive, involves threats, and is played for laughs at least initially. On the other, Bolin is clearly supposed to be the sympathetic one, and Eska is portrayed as dangerous because of her obsession and the lengths she'll go.
The 1920's environment and the Equalists' rhetoric about overthrowing the ruling class mirrors the revolutionist organizations that sprang up in industrializing countries during the late-nineteenth/early-twentieth centuries.
In "The Revelation" the staging of Amon's removing the bending of the leader and members of the Triple Threat Triads is set up like a public execution, a scene which is inevitably repeated when he does it in later episodes - when the Equalists start debending people in bulk it is presented in the manner of methodical mass executions.
Part of the backstory of Tonraq and Unalaq, Korra's dad and uncle, is disturbingly similar to Iroh and Ozai's backstory: a younger and more ambitious little brother eventually "replaces" his older brother - a more calm and kind person, a retired soldier and legitimate heir- as leader of their people. And like Ozai, Unalaq orchestrated a plan to remove his older brother from his birthright to the throne.
The Book Two episode "Peacekeepers" revolves around the debate of whether or not "the United Republic" has a right to invade another country just because a "cultural center" was violently attacked by attackers who may or in fact may not actually be from that other country to begin with. The War on Terror parallels are there.
The Earth Queen's complaints about the Fire Nation colonies taking land from the Earth Kingdom to make the Republic parallels 19th Century China's troubles when Japan and the Western Powers began snatching major port cities for trade. You could even say her insistence that Republic land is Earth Kingdom land mirrors the One China Policy in the PRC.
Also Korra during the climax of A New Spiritual Age rides the dragon bird spirit.
Dreaming of Times Gone By: Given Korra's spiritual shortcomings, the best Aang can manage (until the Book One finale, anyway) is to show her relevant flashbacks from his own life in an attempt to warn her about bloodbending and Yakone's legacy as opposed to simply talking to her like Roku did with him.
Jinora relates a story she read in a historical novel where a princess was unable to be with the man she loved, so she burned down an entire country via dragon and then jumped into a volcano.
Jinora: It was so romantic!
In "Endgame," Tarrlok, and he takes Noatak/Amon with him. There's also reason to believe Korra was considering it.
In the Book 3 finale, after being outnumbered by Bolin and Mako and proclaiming he will never go back to prison, Ghazan decides to use his lava bending abilities to bring the whole cavern crashing down in an attempt to take them with him. Bolin and Mako escape.
Dysfunctional Family: Seems to be somewhat of a theme. Even the idealistic members of the old Gaang didn't all go on to become parents of the year after starting their own families.
According to Bumi and Kya, Aang pretty heavily favored Tenzin at the expense of his two non-Airbender children, to the point that the two older siblings still harbor some resentment, especially in the face of Tenzin's idolizing of Aang.
Korra's uncle and her father hate each other. At first, it seems, they just don't get along because of a clash of personalities, with Tonraq the brash, physical type and Unalaq more in touch with his spiritual side. Tonraq's banishment didn't help either. However, their mutual dislike goes much deeper than that. Turns out Unalaq was responsible for Tonraq's exile from the Northern Water Tribe. Oh, and he's trying to unleash an evil spirit to destroy the world.
Tarrlok's and Amon/ Noatak's father was a super-powerful bloodbending crime lord and all-around nasty piece of work.
Toph's two daughters, Lin and Suyin, aren't on speaking terms. Though Su wants to reconcile, Lin is still bitter about something from their youth. While Lin followed her mother into the Republic City police and Su was a bit of a wild child before settling down, neither one really measured up to their mother's expectations. Things came to a head when Lin apprehended a group of thieves and found Su as their getaway driver. Lin apprehended her sister but Su cut the cable, permanently scarring her sister's face. Toph's response was to tear up Su's arrest report and make Su leave Republic City. Neither was pleased with that outcome. Also, they're half sisters, and neither knows their father.
Surprisingly, one of the least dysfunctional families belongs to Bolin and Mako, who only just found out they even had a family due to chance on their trip to Ba Sing Se. The two orphans are immediately welcomed into their father's extended family with open arms.
Throughout season 2 Korra had been acting like a loon in regards to Unalaq's occupation of the Southern Water Tribe, even going behind Raiko's back when he refused to get involved and trying to make General Iroh intervene. But after the dark spirits show up and Korra says Unalaq is behind it Raiko instantly believes her, despite lacking any actual proof.
Averted in season 3 when they try to get the new airbenders to devote themselves to the culture of the air nomads. Absolutely no one takes them up on their offer, except one boy with no family who had a choice between that and jail.
There is a massive factory hidden beneath the Sato estate.
Chapter nine shows that there is an entire underground infrastructure that the Equalists have built across the city, with transports, storage facilities, factories, training areas and even a private prison.
In season 3, it turns out all the new Airbenders being discovered in Ba Sing Se are being imprisoned in some sort of underground facility by the Dai Li. The Krew initially assumes this base to be the old Dai Li facility under Lake Laogai and head over there to investigate and via Jinora's astral projection ability discover the Lake Laogai facility has long since been abandoned and flooded. The Airbenders are actually being held in a new Elaborate Underground Base under a new temple the Earth Queen is constructing. Tenzin even notes that Ba Sing Se lends itself well to this type of base, as it has numerous catacombs, sewers, and tunnel systems that can be repurposed as this should the need arise.
Eldritch Location: The darker parts of the Spirit World, especially the Fog of Lost Souls, a spirit manifesting as a fog that drives anyone within the fog to utter insanity.
Electric Slide: In "Welcome to Republic City," the metal-bending police use this to easily chase criminals on the run.
While largely continuing its predecessor's formula of tying a person's eye color to their home nation and bending element, there are some aversions in multicultural Republic City. The firebender on the pro-bending team the Rabbiroos has green eyes and one of the metalbender cops has amber eyes, for example. Tenzin's three kids are airbenders, but the girls have brown eyes.
The three main characters — Korra, Mako, and Bolin — play this trope straight. Korra has aqua blue eyes and is natively a Water Tribesman, Bolin has leaf green eyes and is the earthbender, while Mako has amber eyes and is the firebender. Mako and Bolin are a fire and earth bender of the same parents, so while they play the individual eye colours straight, they are also an example of the multicultural nature of Republic City.
While not a bender, Asami is definitely of Fire Nation descent given her name and hair color (her father looks straight out of the Fire Nation) yet she has green eyes, a mark of the intermarrying of ethnically Fire Nation and Earth Kingdom citizens in the Fire Nation colonies.
In Book 3, this trope is totally averted for the new airbenders borne of the Harmonic Convergence. After this point, many non-benders of all ethnicities start obtaining the ability to airbend out of the blue. The majority of the new age Airbenders are of Earth Kingdom ethnic descent, since the Earth Kingdom is the largest (and by extention, most populous) nation, with likely the greatest amount of non-benders pre-Convergence. Thus, we see many airbenders with green and brown eyes, and the occasional marine-eyed one.
Elemental Punch: Tahno tries a waterbending-enhanced uppercut on Korra in "And the Winner Is...", though he fails to connect.
Elite Mooks: The chi-blockers, who unlike the gloved Equalists are able to match benders in an even fight—and come out on top.
Thanks to his allegiance to Vaatu, Unalaq favored was granted the ability to command Dark Spirits, who, unlike Unalaq's human soldiers, are invulnerable to bending or physical attacks.
The Metal Clan, especially compared to the White Lotus and the Dai Li. While all three get banged up when the Red Lotus come calling, the latter two get trounced by the villains in short order while the former come out of their engagements with all their members alive and standing. And contributing to the heroes' strategic victory in The Terror Within.
The Empire: The Earth Kingdom now has traits of this seventy years after the Hundred Year War. The Earth Kingdom is a despotic autocracy ruled by an evil, tyrannical earth queen. The Queen managed to more or less centralize her authority and asserts it on all the kingdom's lands, except for Zaofu, which seemingly escaped her sphere of influence.
Played even straighter in Book 4 where Kuvira takes over and declares a new Earth Empire.
Empty Promise: Tenzin tells his children "everything's going to be fine now" in "Turning the Tides".
Endangered Species: As said by Jinora in "Original Airbenders", the sky bison are now endangered species. Though it doesn't stop poachers from catching the babies for the Earth Queen to dine on.
The End of the World as We Know It: Every ten thousand years, Raava and Vaatu fight to become the dominant force for the next 10,000 years. If Vaatu wins, this would be the result.
The Triple Threat Triads are an actively multi-ethnic bender organized crime gang. In "Welcome to Republic City" Korra meets and beats a Power Trio of protection racket enforcers consisting of a waterbender, earthbender and firebender respectively. Other Triad groups, such as the Agni Kais and Red Monsoons, avert this by being element-specific.
The Equalists are gender and nationality neutral, so long as you're a non-bender.
Same goes for the Red Lotus, or at the very least Zaheer's gang of criminals, which not only includes all the three types of benders including airbending once Zaheer himself gains the ability after Harmonic Convergence but also has an equal gender split with two men (Zaheer and Ghazan) and two women (Ming-Hua and P'li). And Zaheer himself is a non-Bender as well again, before Harmonic Convergence made him an airbender.
Eskimo Land: The Southern Water Tribe city at the South Pole, home of Avatar Korra, her parents, and her Waterbendering sifu, Master Katara.
Raava and Vaatu to each other (depending on perspective). Unalaq becomes an anti-Avatar after bonding with Vaatu.
Book 3 introduces a ragtag team of talented misfits composed of Benders of various types led by a bald airbender who was imprisoned for several years, albeit in a prison instead of an iceberg. Zaheer's team even has a female Bender with a disability, but it's not having arms instead of being blind, like Toph.
In Book 1, a lot of villains try to pit themselves against Amon. Unfortunately, no one, not even Tarrlok, could compete.
In Book 2, The dark spirits are technically enemies to everybody, especially since their leader, Vaatu, is an Eldritch Abomination who wants to wipe out human civilizations and plunge the world in an era of darkness. This is averted with Unalaq and the Northern Water Tribe Military, who are allied with them. Varrick on the other hand, tried to mastermind a war against Unalaq using extreme methods to make profit, but failed to take into account Unalaq's alliance with Vaatu. As a result, Varrick is the only villain who ends up opposing them alongside the heroes.
Evil Laugh: Unalaq - both in the Nuktuk mover and in the actual story.
Evil Makeover: Eska, briefly, in "Peacekeepers". Not that Eska was exactly good before.
In Book One, Amon deliberately goes after every antagonist who isn't working for him (the Triads, Tahno, and Tarrlok). This is part of a plan to get public support by casting himself as a hero for punishing the wicked.
In Book 2, while Varrick was right in saying Unalaq was up to no good, the former cared for no one but himself. He only went against Unalaq, just so he can magnify tensions created by Unalaq's arrival, and plunge the whole world into a war he could profit from.
In Book 3, Korra is captured by the Earth Queen and the Red Lotus goes to Ba Sing Se to rescue her (so that they can use her for their own ends). In addition, taking out the Earth Queen is one of their goals.
Exact Words: In "A Leaf in the Wind", Tenzin tells Korra she cannot watch a pro-bending match. When he catches her enjoying one on the radio, she points out that he never said she cannot listen to one. Tenzin, of course, points out that it's a violation of the spirit of the order, if not the letter.
Expository Hairstyle Change: Along with Korra's Important Haircut, Mako, Bolin, and Asami get new hairstyles in Book 4 which show that they've grown and matured in the past three years. Mako's spiky hair becomes smart and professional, to suit his role as a bodyguard to a world leader, and also to more sharply contrast with said world leader's foppish nature. Bolin also gels his hair into a smarter look after Kuvira insists it makes him look "intelligent and professional," although the fact he retains his curl at the front, and his "duck-butt" hair re-emerges when Opal ruffles his hair implies that he is still the same person underneath. Asami now wears her hair in a ponytail, indicating that she has grown into her role as business mogul. Also, Jinora, Ikki, Meelo, Eska, and Desna all have longer hair in this Book.
Hiroshi Sato is an expy of Henry Ford, a famous industrialist best known for mass-production of cars.
Varrick is this universe's Howard Hughes - an eccentric businessman involved in aviation and film with a love of cookies.
President Raiko is similar in appearance to Sun Yat-Sen, China's first president.
The Earth Queen is based, in her appearance and attitude, on Empress Dowager Cixi.
Eye Am Watching You: In "Welcome to Republic City", Chief Beifong gives this to Korra, index and pinky pointed to her eyes, then Korra. Korra gives one heck of a stink face before throwing the gesture right back.
Face De-Bending with Dignity: All of Amon's victims reacted with struggling and screaming as he prepared to remove their bending until Lin, who after defying his demand that she sell out Korra in return for keeping her bending, simply closes her eyes and calmly accepts what is about to happen.
The Equalists. The chi-blockers wear gas masks, while the shock glove wielders wear a hood and mask combo that obscures everything below the eyes.
Zig-zagged in Book Two. The Northern Water Tribe soldiers are antagonistic, but their faces are fully visible. It's the Southern Water Tribe rebels that cover up.
Facepalm: In "A Leaf in the Wind", Mako does this when Korra makes her first mistake as their team's replacement player in a pro-bending match.
Face Your Fears: Korra tries to face Amon, who absolutely terrifies her, in Chapter 4. It only makes things worse.
Failure Montage: Combined with Travel Montage as Team Avatar travels the Earth Kingdom trying to recruit the newly-awakened Airbenders, and showing Tenzin's utter lack of salesmanship as he unsuccessfully tries to convince each one to come learn the Air Nomads ways.
Fake Nationality: In-Universe example. Bolin, who is of Earth Kingdom and Fire Nation descent, plays Nuktuk of the Southern Water Tribe in the "movers."
Blurring often transitions from the foreground to the background or vice versa, as if someone is adjusting the focus on a camera.
The demonstrations of earth- and airbending in the intro make the "camera" shake slightly.
Korra and Mako's fight against the chi blockers in "The Revelation" features a moment where the "camera" swivels around Korra and her opponent in a panoramic sweep.
False Flag Operation: In chapter 8 Tarrlok, after putting into effect a curfew for non-benders, cuts the power in the Dragon Flats district which would cause the non-bending residents to protest. Tarrlok even branded it as an Equalist rally, and had them all arrested, possibly as a way to bait Amon.
Family-Unfriendly Death: For a show where Never Say "Die" is in full effect, Zaheer's on-screen assassination of the Earth Queen with airbending is incredibly graphic and clearly not painless.
And then the finale of Book 3 has Su Yin defeating P'Li by metalbending a piece of armor around her head just as she's about to use her combustion-bending. We don't see it, but the context makes it pretty clear: P'Li just had her head blown to smithereens. Ming-Hua's death by electrocution was fairly brutal as well.
Fangirl: Apparently, Bolin has a ton of them. During the first pro-bending match's opening in "A Leaf in the Wind", one of them can be heard screaming very loudly "I love you, Bolin!", and Mako's initial attitude towards Korra implies that Bolin brings fangirls to their prep room often.
As an Air Acolyte Pema might have been this when she first became infatuated with Tenzin.
Whether intentionally or unintentionally, Korra's hair being let down in the finale had the fandom swooning!
Fantastic Racism: The Equalist movement claims that benders are oppressing the non-benders of the city. The thing is, they have some legitimate points; there are multiple bending crime gangs which prey on non-benders, the police and army appear to be mostly if not entirely benders, and Republic City is ruled by a council of five benders, one from each nation (Fire, Earth, North & South Water, and Air). On the flip side, Amon talks about "cleansing [benders] of their impurity" and other Equalists have voiced loathing at the thought of benders and non-benders mixing romantically.
Very subtly done throughout Book 2, as certain characters tend to think of members of certain nations in terms of stereotypes:
The fact that Amon falsely claims his parents are killed by firebenders, as well as Hiroshi Sato calling Mako a "firebending street rat" bespeaks a belief that all firebenders are criminals.
Ginger calls Bolin "dumb as the rocks [he bends]". Twice. The second time while claiming to be his girlfriend.
Unalaq and his children seem to consider the Southerners to be uncultured rubes. While Tonraq and Varrick view the Northerners as pretentious snobs who love to order others around. Unalaq's view, however carried a much deeper implication to it; he is resentful towards the rest of humanity in general for their perceived lack of respect towards the spirits since their separation from the spirits since Avatar Wan's time. As a result, he feels that by helping Vaatu, the ancient spirit of darkness, he can create a world where spirits rule and humans are brought to heel.
Air Nomads seem to have a reputation for cowardice - despite Tenzin's bravery, he still gets people, including his own brother, claiming he has a cut-and-run response to confrontation, because it's a "typical airbender move".
Most spirits seem to have an unbelievable amount of belligerence to humans upon first meeting them, even in ages long ago, when Spirits roamed free over most of the world and humans were confined to a few isolated cities.
Fartillery: Meelo first airbends his fart to break his fall in an early chapter, later he weaponizes his fartbending against Equalist mooks.
Father, I Don't Want To Fight: Occurs in Tarrlok'sbackstory. His father is obsessed with teaching him how to bloodbend but Tarrlok hates it and feels it's wrong to do it on the animals they are training on. He finally refuses when asked to bloodbend his brother. In the present day he still refuses to use them until forced to. In a way the same events lead the other brother to also refuse to 'fight'. The brother uses the powers his father taught them to stop *all* bending, not just bloodbending, as Amon to prevent anyone from behaving as his father used to.
The Federation: The United Republic of Nations, a collection of former Fire Nation colonies created as a fifth nation.
Fictional Sport: Pro-bending, where teams composed of one waterbender, one firebender and one earthbender compete against each other, trying to gain the most territory or knock out as many opponents as possible before time runs out.
For the Mako/Korra/Asami Triangle: Played Straight. Despite dating Asami for several episodes, Book One ends with Mako declaring his love for Korra, whom he met first in the second chapter.
For the Korra/Bolin/Mako Triangle: Averted. Despite meeting Bolin first, and even going on one date with him, Korra was never romantically interested in him and explained that she liked Mako from the first time she saw him.
Actually, this can be considered played straight since before Korra met Bolin, she was listening to Mako's match on the radio.But then in season two Mako broke up with Korra and got back together with Asami. After defeating the Big Bads Korra and Mako broke up for good.
Flowers of Romance: In one episode, Bolin and Korra spend a night out together, and later Bolin decides to buy her some flowers. However, he goes to give them to her at the exact time that she's kissing Mako, his older brother. Bolindoesn'ttakethiswell.
Bolin and Mako. Mako is a tightly controlled young man focused on winning the pro-bending prize money to keep himself and his little brother from going back on the streets, while Bolin is more of an easygoing type with a sense of humor and a way with the ladies and an impulsive streak that leads him into trouble.
Tenzin is the responsible sibling to Bumi, his non-bending brother. While Bumi is a competent soldier, he takes his duties and life much less seriously, and is more likely to clown around and tell tale tales of his exploits.
Kya and Tenzin briefly argue over which one of them is the responsible sibling. Kya claims her dropping everything to be with Katara after Aang's death makes her the responsible one, while Tenzin states the fact that she had spent her life prior to that drifting around the world disqualifies her. The Fog of Lost Souls indirectly settles the matter when it shows their worst fears. Kya's is getting tied down and Tenzin's is failing what he perceives as his obligations as Aang's son and the only adult airbender.
Between the two Bei Fong sisters it appears Lin was always the more serious and focused one while Suyin was prone to fooling around and doing crazy things on a whim.
Forceful Kiss/"Shut Up" Kiss: In "The Spirit of Competition", Korra kisses Mako after he explains that he likes her, but he still likes Asami. He kisses her back.
Foreshadowing: One notable example is one of Tarrlok's lines in "Out of the Past." [to Amon] "You fool, you've never faced bending like mine!" Turns out, he not only has, but he's specifically faced his before, and it makes the ensuing Curb-Stomp Battle make more sense since Amon knew exactly what to expect.
In Book 2, Bolin asks Mako for advice on how to break up with Eska. At the end of the conversation, he says "Thanks Mako! I'm lucky you're so good at breaking girls hearts. Huh, Korra better watch out." Come episode five, Mako actually does break up with Korra.
In "Rebel Spirit", he momentarily loses the goofy tone to his voice when Bolin points out he wasn't levitating, and becomes genuinely intimidating. He uses the same tone of voice to greet Mako after he finds out his involvement in the plot.
"Civil Wars" has him leading the revolution against Unalaq, attempting to bribe a judge, and escaping his trial by hiding in a platypus-bear, and he explicitly states his motivation is preserving his wealth. Also his statement that "Honesty is for fools, kid... lie big and run fast!"
"Peacekeepers" has him suggest to Asami that she profit from the war by selling her mecha-tanks:
Varrick: If you can't make money during a war, you just flat-out cannot make money!
While in the beginning of "The Sting," he sabotages an interrogation when Mako appears to be getting too close to the truth.
Vaatu only ever refers to Korra as Raava, showing that he never considers that Korra, a human, has any power beyond what Raava gives her. Which means he also never considers that Korra on her own could stand up to him without Raava.
Bumi has inherited Aang's knack for predicting the future but doing so in such a wacky way that no-one takes him seriously. Most memorably, in "A New Spiritual Age" he tells Tenzin to wake him up if, say, Korra and Jinora's bodies begin floating around and someone needs to catch them. Cue the episode's climax, when Unalaq suspends the two girls' souls in mid-air and very nearly destroys them - until the dragon-bird Korra helped pulls a Big Damn Heroes and carried her away from the battle.
Bumi is able to calm a corrupted spirit by playing his flute, which could have been foreshadowing the events of season 3, where Bumi becomes an airbender, and is shown to have some ability to understand spirits.
Despite being Toph's daughter Suyin lacks her ability to sense the speed of people's heartbeats to tell if someone's lying. This shows she wasn't taught everything her mother knows and her skill is somewhat lacking in comparison. The next season reveals she wasn't able to remove every trace of Korra's metal poisoning that Toph finds.
The Metalbending Corps and Lin are, by definition, master earthbenders, but rely almost exclusively on their metalbending cables rather than their earthbending, even when it would be exceedingly useful. Justified within the city, as the first episode shows, as large amounts of earthbending can wreak havoc with roadways and buildings. Outside the city, there's less of a reason not to use it, besides maybe being something most average earthbenders couldn't easily defend against.
In "Turning the Tides", Asami tells Mako he could have heated the water himself, being a firebender, instead of needing to ask for more.
When fighting extremely powerful Red Lotus members, Mako seems to consistently forget that he can bend lightning, even when it would be incredibly useful. He finally remembers it in "Venom of the Red Lotus", when he kills Ming-Hua by electrocuting her.
Varrick has Mako blamed for the robbery of Future Industries.
In "The Terror Within", one of Zaofu's guards is believed to be behind the Red Lotus infiltrating the city. In fact, the guard is being set-up by Aiwei, who is using his Living Lie Detector ability to interview the guards and can thus blame whoever he chooses. Varrick even makes a Call Back to the frameup listed above.
From the Mouths of Babes: Ikki pulls this on Korra in "When Extremes Meet". She reveals Korra's crush on Mako to Asami, who was unaware of the crush beforehand. Ikki also likes to comment on stuff that isn't appropriate.
The Equalists proclaim they seek to overthrow the oppressive benders, but in doing so prove at least as oppressive themselves.
Amon lambasts the audience at the pro-bending championship match for celebrating benders bullying people. Come the finale, the arena is now full of Equalists supporters, and they cheer on Amon as he bullies the three airbender children tied to stakes for the crowd's entertainment.
After declaring him "weird," Ikki stares at Tarrlok for twenty seconds. The stare continues even after the camera pans to the left to focus on Tarrlok's conversation with Korra, where Ikki can be seen at the right of the shot, still staring at Tarrlok.
Easy to miss, given the gravity of this scene: in "A New Spiritual Age", Tenzin and his siblings agreed to take turns keeping watch over Korra and Jinora in the night at the start of the episode, with Tenzin taking the first shift. At the end of the episode, we see he fell asleep in a sitting position without waking up the next person due to take the watch.