Generational Saga: In Korra, the previous series' protagonists, their children and grandchildren are alternately featured, depicted in flashback or discussed, particularly Avatar Aang's multigenerational family, with his reincarnation Korra narratively treated as a de facto member.
Genericist Government: We know the United Republic of Nations is some sort of a republic, that there's a council overseeing Republic City at the very least, but beyond that Season 1 leaves a lot of details blank.
Gentle Giant: Doubly subverted: Iroh is still on the short side, as he was in the original series, but towers over Korra by dint of her having regressed into childhood.
Gilded Cage: At the start of the series, Korra lived in a lavish mansion, with her only real challenge in life being to learn bending from masters... in the middle of an inaccessible and heavily fortified compound, miles from any other inhabitants of the South Pole—including her own parents. She was not allowed to leave the compound without permission, and had guards watching her at all times, even while taking Naga on a walk.
In "The Spirit of Competition," Bolin does this with bonus Inelegant Blubbering while fleeing the deeply hurtful sight of his friend Korra (who he'd taken on a date the night before) kissing his brother Mako.
Opal also runs out in tears after Lin yells at her. For added cute, the fact that she's wearing Metal Clan jewellery means she jingles as she runs away.
Gone Horribly Right: At the beginning of Book Two, Bolin attempts to flirt with Eska. Surprisingly enough, Eska almost immediately engages in a relationship with him. Unfortunately for him, though, Eska has all the warmth and charm of a glacier, her definition of "boyfriend" appears to be "slave", and she has some scaryYandere tendencies beneath her emotionless mask.
Bumi suggests that Tenzin try being a Drill Sergeant Nasty to motivate the Airbender recruits. So he does. Too bad Bumi forgot he was one of the recruits, too.
Good Parents: Korra's parents, along with Tenzin and his wife.
Gory Discretion Shot: P'Li's death in "Enter the Void" has a rather conspicuous cut, not even playing the sound of an explosion. It just cuts from the moment before to the reaction shot.
Gosh Darn It to Heck!: Enforced, as it is both a family show and Justified as it's set in the equivalent of the 1920s. A frustrated Tenzin, for instance, mutters "criminy" at one point.
And in the first half of Book 2, Unalaq and the northern water tribe are at first not shown as inherently evil, just overzealous about uniting the water tribes and willing to go to all lengths to save the water tribe from dark spirits, while the Southern Water tribe rebels and Varrick in particular use morally questionable methods to fight back. This is Inverted when Unalaq's real plans are revealed, that he and the Northern Water Tribe military are allied with Vaatu and the Dark Spirits, placing them on the evil side.
Definitely very gray morality is present in Korra's conflict with Raiko. Both positions are always shown to be right, but they're in opposite directions, which creates a wedge between both.
Group Hug: The Fire Ferrets have one in "The Spirit of Competition" after defeating the Rabiroos.
Despite their badass introduction, the Metalbending police seems to be incredibly incompetent as a security detail, allowing dozens of people to smuggle weapons into the Pro-bending Arena and getting curbstomped by said weapons, even though they knew full well that the Arena would almost undoubtedly be attacked. Later in the series, they are incapable of protecting the United Republic's president or even notice that that very same arena is again under attack.
While she has not appeared in-show, Toph Beifong is considered a Living Legend, as the inventor of metalbending, founder of the RCPD, mother of the Metal Clan's founder, and an all-round visionary and genius. Also, she's blind.
Ming-Hua, the Red Lotus' waterbender, has no arms, relying instead on two large watery tentacles, which she uses to swing around, as a bladed weapon, and even to drive a car.
The airship captain in "Long Live The Queen" has a hook-hand. Though he doesn't do any fighting, he stands up to Korra without so much as flinching.
He Is Not My Boyfriend: "A Leaf in the Wind," when Bolin lies to Toza to let Korra backstage, Korra feels the need to correct him:
Bolin: So, you see, we're together... Korra: Well, not together-together, more like friends. Bolin: Right, right, friends... no, I didn't mean to imply that... Korra: Oh, you implied it.
Healing Hands: Korra is one of the water-benders who have the ability to heal, having learned it from Katara.
Heart Symbol: Mako has them fluttering around his head after meeting Asami, but more subtly, the table and chairs they sit at on their first date are lit in such a way as to strongly imply a heart◊.
One between Korra and Mako in "A Leaf in the Wind" after they win the pro-bending match.
Bolin and a minor unnamed bender share one of these when the bender is led away to have his abilities removed by Amon in "The Revelation".
Heroic Sacrifice: In "The Turning of the Tides, " Lin buys the airbenders time to escape. When captured she refuses to tell Amon where Korra is hiding, and has her bending removed.
Hero Insurance: Subverted in the premiere. Though she assumes she has leeway, Korra learns the hard way that being the Avatar is not a license to dish out vigilante justice and smash property. Double Subverted later on.
Hijacked by Ganon: In universe example; in the first episodes of Book 2, it seems like Chief Unalaq is the Big Bad. However, it's eventually revealed he actually is working for Vaatu, a Predecessor Villain who was introduced later on, but whose first appearance chronologically happened before the original series, and who had only been seen in flashback at this point.
Bolin performs this in "The Spirit of Competition," after getting smacked by a stray earth disk. Unusually, it actually is his shoulder that's injured, complete with ugly bruise.
General Iroh does the same thing in Endgame, even though his injury is lower, against his bicep.
Hollywood Density: The mecha-tanks are said to be made of pure platinum to prevent metalbending, disregarding how mind-bogglingly heavy this would actually be. Given that metalbending is achieved by manipulating the impurities, any sufficiently purified material should suffice for this purpose. Titanium would have made more sense, being more common and far less dense for its relative strength.
Hope Springs Eternal: The world was far from being in balance when Wan died. However, somewhere among those who would be the Air Nation eventually, a child would be born who would continue what Wan started. The world may be out of balance but the hope for restoration continues to thrive.
In "A New Spiritual Age" Korra must decide between opening the spirit portal for Unalaq or watching Unalaq corrupt and destroy Jinora's soul. Furious, she picks the former.
In "Long Live The Queen", Zaheer offers to trade the location of the airbenders to the Earth Queen in exchange for her turning over Korra to him. This deal never comes to fruition.
Huddle Shot: Used "Spirit of Competition", when Mako tries to build up confidence for the upcoming tournament.
Hufflepuff House: The other three members of the city council. The only two actual voices in the council are Tarrlok and Tenzin, and the rest of the council always sides with Tarrlok. Even when he changes his mind.
Tenzin is as serious and staid as Aang was carefree. Despite this, he still feels enormous pressure to live up to him - his main lesson in season 2 is "Be Yourself".
Although Lin shares Toph's toughness, she's very strict about enforcing the law and has no patience for the Avatar's vigilante justice.
Asami refuses to join the Equalists with Hiroshi.
Tarrlok decided to take over Republic City through legal means, rather than from the criminal underground.
Su had too much freedom as a child and so raised her daughter with too little. Fortunately, she realised it was for the better for Opal to realise her potential as an airbender.
I Can't Believe I'm Saying This: When Amon tried to intimidate Republic City into not holding the pro-bending tournament finals, Korra wanted the finals to be held despite Amon's threats. Chief Lin Bei Fong, despite how she usually feels about Korra, agreed with her.
Played for laughs in Book 2. When the caretakers of the Southern Air Temple praise the next generation of airbenders, Pema looks to her currently bickering kids and less-than-enthusiastically repeats the sentiment.
One of the themes of Book 2, actually. Tenzin and Korra in particular are forced to come to terms with the fact that they are their own person and not simply the roles that are placed upon them (progenitor of a new generation of airbenders and the Avatar).
I Need a Freaking Drink: After going through hell and back trying to escape a giant desert-shark in the Si Wong desert, the crew of the airship carrying Korra finally arrive at the Misty Palms Oasis... only to find Zuko's dragon napping right in front of them. Small wonder that this trope is the captain's reaction.
Instant Expert: Deconstructed in season 3. Zaheer picks up airbending very quickly, but when he fights against Tenzin, an actual master, he gets curbstomped thanks to Tenzin's years of experience. Downplayed with Bolin, who picks up lavabending quite quickly, but aside from a few basics it's not that different from earthbending.
Insult of Endearment: After warming up to Wan, the aye-aye spirit affectionately calls him "Stinky".
Inverse Law Of Utilityand Lethality: Especially in Book 1, people get casually electrocuted A LOT. The Equalists have their electrocuting gloves, mecha tanks, and other implements; Mako (and other firebenders, presumably) have lightning; and although characters are definitely in pain when hit, everyone shakes it off like nothing happened. Particularly striking for Amon, who takes a full dose of lightning from Mako at point-blank range in the season finale, and walks away from it like he just took a shot of espresso.
Ironic Echo: During the infiltration of Sato Manor, one metalbender cop was assigned to watch over Asami, Mako, and Bolin. When he tells them to stay put until Chief Beifong returns, Mako and Bolin incapacitate him, and Bolin delivers this spiteful reprise:
Toph, a boastful, destructive, anarchist hustler became a police chief? That's really challenging to comprehend.
Toph points out some of the issues she has with the relationship that she has with her parents in the first series. Unfortunately, she seems to have, in her own way, committed some of those same mistakes. In her efforts to not be overbearing like her parents, Toph gave her children a lot of space and freedom. This lead to neither Toph or her children feeling like they received the love and validation they needed. Guess she can't give away what she never got.
The present generation of the Beifong family seems to have an element of this. While her sister eventually ran away and found the love and validation she needed but didn't get at home, Lin played things close to the vest, following in her mother's footsteps but reaping relationships that yielded none of the validation and love that she wanted, even from her own mother.
In Book 3, Harmonic Convergence randomly gave non-benders all around the world the ability to airbend. Very few of them have the time or interest in becoming full-fledged Air Nomads. In fact, only one Air Acolyte has been shown to have gained airbending, and he's a little on the off side.
It Only Works Once: When Korra first fights Equalist chi-blockers, they use smoke bombs to disorient her and cover their escape. The second time she faces chi-blockers she encases the smoke bombs in water and freezes them to contain the smoke.
In Touch with His Feminine Side: Bolin, who despite his bulky physique and athletic profession, is extremely emotional and sensitive, and loves make-overs.
Amon is afraid of turing Korra into a martyr and wants to gain public support before going after her. Even afterwards, he doesn't want to kill Korra because he prefers to leave his enemies alive to suffer.
Unalaq needs Korra's help to open the Spirit World portals.
Tarrlok is using his task force to score political points, but the Equalists are a militant revolutionary group openly advocating the violent overthrow of their country's government and the extermination of bending. Some sort of official response is necessary to that existential threat and Tarrlok is the only council member offering a plan.
Similarly, while the Equalists are depicted as being far too extreme, they wouldn't have been able to raise an army if benders weren't abusing their powers on the scale we saw.
While Korra acts rather rude about it in the start of Book 2, she does have a very valid point when she calls out Tenzin and her father for constantly bossing her around and treating her like a child.
While the humans from Wan's home village are destructive towards nature and attack spirits on sight, the spirit wilds are shown to be actively hostile to human life and the spirits have no problem attacking humans even though, by all indications, even a human with elemental powers doesn't have a chance of killing a spirit. The spirits aren't natives, either, having migrated from the spirit world, and its their presence that forced the humans to retreat to the lion turtles in the first place.
Just Friends: In "The Spirit of Competition," the Sibling Triangle of Bolin, Mako and Korra articulate their feelings towards each other in various ways. After resulting interpersonal tensions nearly cost them their place in the finals, the three settle back into a mutually friendly dynamic, with the larger underlying Love Dodecahedron unresolved.
Kaiju: Some of the larger Dark Spirits fall into this category, especially The one that swallows Korra.
the Dark Avatar Unalaq turns into one, who is then defeated by a Korra-Kaiju in the bay of Republic City.
The sandshark that attacks Korra and Asami in the Si Wong Desert.
Kangaroo Court: The trial in the third episode of the second season. Korra's father is found guilty of treason (a capital crime) simply because the meeting that led to the rebellion was at Korra's father's home. No defense was allowed, and the prosecutor/judge asked nothing but leading questions. And it's quickly revealed that the judge was ordered to make his decision by Unaloq in order to manipulate Korra and still get the rebels out of the way.
Karma Houdini: Varrick starts and escalates a war for profit, steals from a business rival, and tries to kidnap the President ... and only stays in prison - a cushy prison he designed ''for himself'' - before almost immediately breaking out.
The reason Lin Bei Fong hates her younger half-sister Suyin so much is because Suyin indirectly helped Triads commit crimes when she was younger, one of which Lin busted her for and which led to Lin getting the scars on her cheek from Suyin sucker punching her - even if it was accidental - and mama Toph's response to this was to throw away Lin's report and send Suyin to live with her grandparents instead sending her to jail. To say that Lin held a grudge against Suyin for escaping punishment is an understatement.
Ki Attacks: Like in its predecessor series, bending has a basis in the eastern theme of Chi, so all bending is technically ki attacks of an elementally aligned nature.
The first public victims of his bending-removal ability are the leader of the Triple-Threat Triad gang and three of his bender thugs.
Amon's second group of victims is the Wolf-Bats pro-bending team, which had just won the championship through bribery and flagrant cheating.
In Chapter nine, he takes out Tarrlok, the Sleazy Politician who was making a grab for power on the backs of Republic City's non-bending population.
Zaheer kills the current Earth Queen, a bitchy tyrant who forcibly conscripted Airbenders into her army, heavily taxed her citizens to support her luxurious lifestyle, and sponsored Sky Bison poaching to satiate her taste for exotic meats.Very few people in-universe are upset over this; even Korra is more angry about the lengths Zaheer has gone to fulfill his goal, and the chaos and destruction that resulted rather than the Queen's death.
Land of One City: In the time of Avatar Wan, humans lived in isolated cities far from each other. So far and with such dangerous terrain between them the idea of other humans living outside the city is considered a legend and not possible. And these cities are on top of lion-turtles.