Improv Fu: Jyuza gave Raoh one hell of a Humiliation Conga with a fighting style he invented on the spot. The fight ends with him stealing Raoh's horse, Kokuoh.
Inertial Impalement: One scene shows the villain's fortifications, including sharpened trees thicker than a man's arm. Later on the downtrodden villagers storm the villain's base, and one guy is shown to have somehow impaled himself at least three feet on one of the stakes.
Infant Immortality: Although children and even infants often died in the manga (along with a few dogs), the TV anime often rewrote such scenes so that the child escapes from harm's way with Kenshiro's help (the most prominent examples being Taki, Bat's adopted little brother who gets shot by one of Jackal's men, and Ryo, the kid in Shuu's hideout who ate bread poisoned by Souther and his men).
Informed Ability: There are villains who brag about their unstoppable fighting styles whose power we never see onscreen, though a good load of them do manage to show it off. The most ubiquitous example has to be Souther's Tensho Juuji Hou attack, which supposedly can cut through stainless steel, but only scratches Ken's shoulders a bit and got a lot of hype beforehand. Granted Ken's Made of Iron, but still. (It's like Musou Tensei in that he passes through Ken's attempted counterattacks, but no mention is made of why this doesn't work when he jumps right into Ken's successful Tenha Kassatsu.)
Kenshiro once got hit in the head with a solid stone pillar as big as he is and remained completely unfazed (the pillar shattered to pieces). So it is easy to see how an attack that can cut stainless steel might be not a big deal to him.
Intangible Man: One of the effects of Hokuto Shinken's ultimate technique Musou Tenseinote "Nil-Thought Rebirth".
I Want My Beloved to Be Happy: The manga's final volume has Ken and Bat both trying out the I Want My Beloved to Be Happy suit with Lin: earlier, Kaioh had pressed the pressure point Shikan Haku on Lin's back that would cause her to fall in love with the first man she saw upon waking — expecting that it would be a scummy bandit or a lowly beggar, anyone but Ken; nevertheless when she wakes, it's just Ken and Bat (who'd learned of Shikan Haku — important point there). Bat was aware of Lin's love for Ken, but Ken was sympathetic to her for all that she'd been through and instead wanted her to live peacefully, so he rode off to ensure that Lin would fall in love with Bat instead. Bat makes a show of going along, but at their wedding he's unable to fully commit — feeling that it's not right for him to be getting the (sincere) love compelled onto her, so in an even more extreme case, he actually causes retrograde amnesia in her, then in an incredibly cockamimie plot actually attempts to "guide" the rebuilding of memories in an attempt to cause her to fall in love with Ken all over again instead... by the end though, it fails when Ken and Lin both regain their memories, and in her case remembering her love for the now-dying Bat. While Ken promised to Bat that he would go off with Lin, he secretly pressed healing points on Bat before leaving without her... leaving her a welcome surprise.
Jabba Table Manners: In a world where basic food and fresh water can literally cost you an arm and a leg, any character who eats gourmet food can automatically be labelled as a wasteful villain. Souther in particular is an exceptionally vile example of this trope. Shisuka from Kenshiro Den is an even more literal example than Souther, though the first arc of the manga (post-Kaioh) had Kouketsu.
Kiai: Kenshiro's battle cries mimic those of Bruce Lee. Not to mention that in the anime, he looks like him too (at least in the early episodes). In the manga though, his face, hair, and clothes all very closely resemble Mel Gibson's character, "Mad" Max Rockatansky in the Mad Max films — then, when he went off to Shura, Sylvester Stallone.
There's also his famous "ATATATATATATATATATATATATATATA!" kiai, which he uses when he's busting out his Hokuto Hyakuretsu Ken on some sorry bad guy
Ki Attacks: Hokuto Shin Ken uses Touki to strike opponent's pressure points with out contact.
Gento Ko Ken specializes in using ki to destroy enemies on the cellular level via burning or freezing.
Kick the Dog: A constant, neverending stream of atrocities designed to make you feel that the villains deserve every last bit of righteous ultra-violence Ken can lavish upon them. One bad guy even literally kicks a dog — a cute puppy to be precise.
Kill 'em All: Fist of the North Star is a long-running manga with a massive and diverse cast of characters... but if they aren't named Kenshiro, Lin, or Bat, don't expect them to stick around for long. Story arcs where everyone but our protagonist ends up dead in a heap are extremely common.
Killer Yoyo: Mamiya uses two of them, and looking damn fine while doing so.
Limited Animation: Whenever Ken walks, more often than not the animators just take a static frame of him and wave it up and down. Leads to Narm in some cases, such as the HILARIOUSLY bad special effect in episode 23, where we see Ken from an exploding Mook's point of view, and it's painfully obvious that the animators just waved Ken's picture around in the background. There's also the episode in which Ken kills Devil's Rebirth: It just shows him from the back as he punches, while Devil's body goes past up. It's the funniest Green Screen effect ever.
Lends itself to unintentional Narm Charm at times. For instance, when Kenshiro confronts Amiba after the later epically fails at copying Hokuto Shinken, he is supposed to step up right into Amiba's face. However, the animation for this scene is simply a still frame of Kenshiro leaning forward being slid up next to a terrified Amiba, and it comes off as even more inappropriately humorous (possibly because the immediately preceding scene was already fairly Bloody Hilarious).
Linear Warriors, Quadratic Wizards: Inverted with Hokuto Ryuuken, which uses magical incantations heavily in its fighting style but is explicitly stated to be inferior to Hokuto Shinken, which focuses on physical attack and pressure-point techniques.
Loads and Loads of Characters: strong characters with unique fighting styles are introduced, only to be killed off within the next volume or two. Think Bleach, if people died.
Some of them are given bit more screen time in Toei's anime version, like Raiga and Fuga, Koryu, Hyui and Shuren, Shoki and Nagato to name a few.
Look What I Can Do Now: Long training sequences are generally avoided, but this does not stop characters from suddenly unleashing new abilities that they either learned spontaneously, or perhaps had known all along.
Love Freak: Shu, Yuria, to an extent. Lin also counts as well.
Mad Bomber: Jackal and his gang are awfully fond of dynamite sticks as weapons.
Made of Iron: If you're one of the more powerful fighters in this series, you are virtually immune to damage. For example, Kiba Daioh, a relatively low-level martial artist villain, used a technique which literally transformed his skin into steel, so that when super-strong Kenshiro used a massive steel beam to bludgeon him, the beam was bent into U-shape without doing any damage. Then Kenshiro struck a pressure point which effectively canceled the effect, allowing Ken to break Kiba's spine during the second try.
Martial Medic: Kenshiro can manipulate pressure points to heal as well as harm.
Meaningful Name: Toki, who shares his grace with the ibis he was named after, and Souther, a slightly more convoluted example. The southerly winds. What birds fly on. Birds like the Nanto style is inspired by. Meaning he is at the root of all Nanto schools, as the emperor. Like that wouldn't get to his head... And then there's Kenshiro himself, whose name translates to something like "Fourth Son of the Fist."
Mega Manning: The first clue that Ken is running on The Power of Friendship is when he starts to inexplicably use attacks that belonged to fallen allies. He also explicitly claims that practitioners of his style can duplicate the attacks of any other style, though he's the only practitioner shown actually doing this. Also, Raoh runs a giant prison full of martial artists for the sole purpose of stealing all their secrets. There's not enough detail to determine whether it's this or Awesome by Analysis, but analysis really doesn't seem like Raoh's strongest suit.
Men Don't Cry: Completely and wonderfully averted in this franchise: violence and brutality be damned, Fist of the North Star is frankly one of the most sensitive and warm-hearted anime franchises of the 1980's.
Mighty Glacier: Mr. Heart practically defines this, in both the show and the PS2 fighter. Another large character, Fudou, does basically nothing but ride this trope.
Monster of the Week: The anime version of the Southern Cross arc, and to a lesser extent the Goshasei and Shura arcs, gave Kenshiro more weekly villains than the ones he fought in the original manga.
Monster Sob Story: Told by both Souther and Kaioh to Kenshiro right before their final battles, when there's no time left for the reader to watch them grow as characters or sympathise with them. Though the week-to-week short term plotting of the shounen manga industry is probably to blame here.
Mood Whiplash: The over the top ways in which evil, evil people die insanely sometimes verges on black humor, partially from Narm and partially from their cowardly antics. Then there's the time Ken's cute sidekick gets splattered with gore in the middle of a brutal fistfight to the death by way of comic relief. However, this trope is here for one man: Jyuza. In the manga, his introduction, a digression from a hopeless war the established characters are fighting, takes its sweet time showing us a piece of his happy-go-lucky, adventurous life. Then he is called out to fight, and its back to the nightmare for the audience.
Mook Horror Show: When Ken annihilates Jackal and his gang. Fittingly, the episode is entitled "I Am Death Itself! I'll Chase You to the Ends of Hell!"
Motive Decay: After his parents were murdered and his sister sold into slavery, Rei didn't bother with his role as the Star of Justice until after meeting Toki.
Souther's original traumatic backstory was omitted in the Shin Kyuuseishu Densetsu movies, leaving him as a one dimensional villain.
Mukokuseki: Racially ambiguous characters, names written in katakana, and lack of Japanese signage make many readers confused about where the story is set. But during the Southern Cross arc of the manga, Bat specifically states that Shin's gang rules the former Kanto area.
Mugging the Monster: This happens all the damned time to Kenshiro and the other major badasses of the series. You'd think the mooks that these guys come up against would know not to mess with them, especially after seeing their fellows exploded messily.
Muscles Are Meaningless: Partially averted. Almost all serious martial artists are musclebound bruisers (and about half of them, including Kenshiro, are much taller and more massive than average inhabitants of the postnuclear desert), but, on the other hand, there are a lot of really superhumanly big people in this series (mutants? genetically engineered? it is never explained where all these five-meters tall humans came from), but their giant size usually does not help them much, even though some of them are accomplished martial artists in their own right. Buronson likes toying with this one. Hokuto's breathing techniques effectively embody this trope, but apparently most of those giant mookswere about as tall as Toki.
My God, What Have I Done?: Several times, especially Raoh with Yuria. Arguably Shin. Certainly Kaioh. Fortunately in Raoh's case it was "My God, What I Could Have Done."
The Narrator: Shigeru Chiba, who also voiced a few of the villains, pulls double duty here. He also gets gradually more excitable as the TV series goes on; as an episode of Trivia No Izumi pointed out, he starts off doing the next-episode previews in a rather stern voice, but by the final episode he's screaming the narration at the top of his lungs. It originally started as an in-joke by Chiba; he apparently stopped ramping it up for a while for fear of giving himself an aneurysm, but began doing it again when fans asked him why he wasn't shouting anymore.
Never Forgotten Skill: Close to the end of the series, Kenshirou ends up losing his memory. Despite this, he kills off some thugs with Hokuto Shinken with little effort. Clearly, his skills with the martial art can never be forgotten, even if he has amnesia.
New Old West: Right down to the "stranger walking out of the duststorm into the town" shots and the Morricone-esque mournful-saxophone music of Spaghetti Westerns in the more sad and thoughtful scenes.
New Powers as the Plot Demands: Kenshiro can not only kill or heal people by touching pressure points, but in one episode, he even touches a pressure point that makes a thug involuntarily move his mouth to answer Kenshiro's questions.
Nice Hat: The helmets in North Star are legendary. One notable example is Uighur, who hides whips in his horned helmet (you pull them out by yanking on the horns).
No Celebrities Were Harmed: Toki looks and acts a hell of a lot like a certain Son of God. Not to mention a variety of "cameos," like Mr. T and Hulk Hogan lookalikes (Barona and Bask, respectively) teaming up together, or the Harn brothers who resemble the tag team Legion of Doom, or a Shura who looks like Sloth from The Goonies, or Abida who strongly resembles Gene Simmons... the list goes on and on.
No Hugging, No Kissing: Despite love, or rather fighting for it, being a main theme in the series, not much happens between the Official Couple, Kenshiro and Yuria are shown to be a couple in its purest form, the original manga and anime only had them going as far as holding hands, and yet it is implied they went much further than that, the movies even had Yuria expecting Kenshiro's child; spin-offs avert this by having other characters like Rei, Jagi, Raoh and even Kenshiro's uncle getting hot and heavy with their interests, ironically Ken and Yuria gets no such "step-up" in spin-offs even though they are the original Official Couple.
Non-Indicative Name: Out of the six members of the Nanto Roku Seiken (South Dipper Six Sacred Fists), only five of them are martial artists. Since Yuria has no fighting skills, there's only five main branches of Nanto Seiken.
Norio Wakamoto: Its a small appearance, but the man himself voices Raoh in his first silhouette scene, as well as Shuren. Somewhat altered in that Shuren was a heroic character.
Not Hyperbole: If Kenshiro tells that after he's through with you there will be not one hair left from you, he MEANS it! Southern found out about it the hard way.
Not Worth Killing: Jagi when he was disfigured by Kenshiro. Kenshiro would later regret his decision, as it backfired a lot. (Jagi was the one whose conniving caused Shin to decide that Kenshiro didn't deserve Yuria, and Jagi's later modus operandi was to drag Kenshiro's name through the mud.)
Playing with Fire: Shuren plays this trope note-for-note with one interesting variation: instead of being supernatural, his fire skills are described coming from expert use of chemicals combined with a high level of martial arts.
Plot Tumor: The original manga focused primarily on martial arts (some hardcore, some zany) and the Ki Attacks were a rare occurrence. In the manga's second run, we are introduced to Gento Ko Ken - a martial art based almost entirely on Ki Attacks.
The Power of Friendship: In his climactic battle against Raoh, Kenshiro reveals that he has the power of all his friends behind him. Subverted earlier when Rei, attacking Raoh, tried to invoke it. Really bad timing, Rei.
The Power of Love: Raoh, meanwhile, is only able to learn Hokuto Shinken's ultimate technique, Musou Tensei, through his love of Yuria and sorrow over her sad fate. Which was My Kung-Fu Is Stronger Than Yours by Kenshiro when he revealed that not only does he have sorrow over Yuria too which gives him as much power as Raoh, he also has sorrow over losing his beloved big brother Raoh! The Power of Love is all over this story. If Raoh and Kenshiro's case wasn't enough, see Kenshiro vs. Souther, which itself is also all about this.
Possibly also how Lynn could free herself from Zaria's hypno-magic spell.
Precision-Guided Boomerang: The Colonel deploys several small, metal, razor-sharp boomerangs (perhaps a deliberate homage to The Road Warrior, which was very influential on the series), as part of his complex martial art. They are all on target, despite him plunging the battlefield into darkness (to make it hard to see the boomerangs!) Ultimately it's revealed he's psychically guiding them.
Pressure Point: 708 of them to be exact, with equal ability to heal as well as kill if the right ones are pressed. More precisely, the vital points used by Hokuto Shinken is known as the Keiraku Hiko, which roughly translates to the "hidden points of the meridian". The rival style, Hokuto Ryuken, uses another set of pressure pointd called the Keiraku Hako or the "destructive points", which has exactly 1109 points.
Pronoun Trouble: The Last General of Nanto and the Heavenly Emperor are both revealed to be female. The former case can be justified, since the Five Chariots were intentionally hiding the Last General's identity to prevent Raoh from going after Yuria.
Psychopathic Manchild: The Fang Bandits, which are an entire group of animal themed Psychopathic Manchildren.