The audience gets to know the kind of person Light becomes when we learn that in the time between acquiring the Death Note and meeting Ryuk, he's already written pages of names within the Note, knowing that they're all dead by his hand. And then he proclaims his plans to use the Death Note to become "God of the New World".
L is introduced as a character when he tricks Light into killing Lind L. Tailor, and then uses various pieces of circumstantial evidence to discover that Light is not omniscient or all-powerful; he does, in fact, have limits on his ability to kill people, and L now knows where "Kira" lives. He also openly taunts Light, becoming the first person in the series thus far to truly make him angry.
The anime introduces Mello and Near in the same scene, having the former freak out in reaction to what he's told while the latter remains calm, nicely setting up the Red Oni, Blue Oni dynamic between them.
From the same series, you have WolfgangGrimmer, whose first major interaction with another character is to offer his shoes to a kid whose shoes were stolen by some bullies, neatly demonstrating both how eccentric and what a nice guy Grimmer is.
Haruko Haruhara of FLCL fame gets this in the first few seconds, just to let the audience (and the characters around her) know that she's insane: After finishing a piece of bread that she was implied to have stolen, she revs up her moped, gives us a smirk and a cry of "Awright! LUUUUUNCHHHH.... TIIIIIIMMMMEEEE!!!!", and blasts off at breakneck speeds, running over our main character (which she doesn't even notice until she stops), completely freaks out about "killing" who she believes to be "Tarou-kun", defying all laws of physics in the process, and then proceeds to give her version of CPR (actually, just planting one long, passionate kiss on the mouth) knocking said protagonist out of shock, proceeding to bean him square on the head with a bass guitar, shake him upside down (even though she had just told the protagonist's friend not to do this) frustrated that "it's not coming out," then proceeding to call him useless and driving off faster than when she arrived.
In Lupin III: Castle of Cagliostro, Lupin and Jigen triumphantly drive off with stolen cash. However, they quickly realize the bills are impressive forgery of the Goat Bills. The disappointment doesn't last long and they just joyfully throw all of the (probably spendable) cash out and decide to find the source of the forgery.
DNA2 establishes Karin by cutting from the highschool drama to an abandoned factory, a huge, round space capsule appearing and her stepping out, her face mostly obscured by the mist and her clothes, giving us a Blasphemous Boast... and then she proceeds to swoon and squee over how awesome that whole thing was!
Yusuke Urameshi in YuYu Hakusho spends his first scene, and in fact the first several episodes, dead. This is far from defining, as he gets better, but the true Establishing Character Moment here is him getting rather irritable at the people gathered around his corpse, even taking a swing at one of the paramedics there to take his body away. He is a ghost at the time, so it really comes to nothing.
All of this happens AFTER he had sacrificed his own life to save a child (more or less...), which goes a long way to establish him as a good-natured thug.
Kurama walking out on Hiei and that other guy after acquiring the magic mirror.
Luffy's first appearances in both the manga and anime pretty solidly define his personality and approach towards life, albeit at different angles. In the manga, we see him as a small child giving himself a scar on his cheek to show how tough he was, and is cheerful in the next scene. The anime shows him bursting out of a barrel cheerfully screaming about his great nap.
Zoro's first appearance in the manga is being tied to a pole, starving for 9 days and smiling. Also, when he eats the dirty riceball that a little girl left him (who he had earlier rescued despite not knowing her and was why he was captured in the first place) and asks Luffy to tell her that it tasted good, you know he's a good guy at heart.
Nami's first appearance in both the anime and manga does this - in the manga, she's running away from some pirates who she's just stolen from, and when Luffy falls out the sky in front of her, she uses him as a scapegoat so she can run away. In the anime, she's sweet-talking a guy on a rich passenger ship, only to sneak off to steal things the second everyone's distracted.
Sanji is introduced serving Fullbody and his date, making advances on the date. When Fullbody tries to get him in trouble in revenge for being humiliated, and ends up spilling the soup that Sanji made on the floor, Sanji beats him up, as wasting food is a Berserk Button for him.
Mihawk is introduced by effortlessly destroying Don Krieg's flagship, already having destroyed the rest of his fleet. When asked why he followed them, he stated it was to kill time.
Captain Smoker gets an interesting introductory scene — a little girl spills her ice cream on him, initially causing him to set his Death Glare off on her. But rather than snarl at her or Kick the Dog he kindly offers to buy her a bigger one. This establishes him as a more morally complex character than many of the other Marine characters in One Piece who doesn't adhere to the Marine's "Absolute Justice" doctrine, and hence mainly serves as a Worthy Opponent later on for the crew.
Ace is introduced as having fallen asleep in a restaurant, while eating and while in the middle of the conversation, making it look like he'd died mid-sentence from spider poison. The first thing he does upon waking up is wipe his face on a lady's dress, wonder why everyone's panicking...and immediately fall back to sleep in the same position as before. His following conversation with Smoker also shows his more serious side.
The first thing Admiral Akainu does onscreen is blowing up a ship full of evacuees that the Marines had promised to spare just because of the slim chance that one of the criminals they were after might be onboard. This happened in Robin's backstory, 20 years ago.
Many of the Eleven Supernovas get fairly interesting reveals. Law is introduced as a level-headed yet creepy pirate who doesn't hesitate to flip off the supernova with the highest bounty.
AdmiralFujitora's gets one in his second scene when he orders a subordinate to count the number of civilians in the coliseum, the city, and the country because "Before counting our enemies, shouldn't we count the number of people we have to protect?"
Kaido.His first act is to jump off a sky island, 10.000 meters in the air, crashing the alliance-party of three of the Supernovas, sinking one of their ships, and devastating the place, from the impact alone. He complains he didn't die, and declared his intent for war with Doflamingo, without even knowing of his predicament. He was bored.
Within minutes of first appearing in Yu-Gi-Oh! 5D's, Crow steals from a warehouse, pulls off a one-turn-kill against a Mook, then flips out some wings on his motorcycle to fly over a ramp to safety. Get used to such moments.
While it may not appear this way at first, the initial appearance of Priscilla in Claymore sets up a lot of what will happen later. We hear that she's a new Claymore who's recently ranked # 2...and then she's late, and when she does show up she trips and falls over while apologizing for being late because of some Yoma. Just as the other Claymores and the audience are prepared to write her off, we look around and see that the alley she just came out of is covered from top to bottom with dead Yoma, which she just plowed through, by herself, without alerting the others. This establishes Priscilla's naive and innocent nature while giving a glimpse of just how ridiculous her powers are, so it's no surprise that she later becomes what may be the most powerful awakened being ever.
Her daughter Fate's establishing moment comes in the second drama CD, when she forms a familiar contract (which she'd been studying secretly) in order to save the life of a dying wolf cub she encountered despite knowing little about animals, but leaves the contract open-ended so that the familiar, Arf, won't disappear. This shows that she's somewhat naive, but also a skilled mage who will do anything for those she cares about.
Before she even makes it to her first audition in Kaleido Star, Sora shows her colors as a spirited and determined youth by chasing down a man who stole her luggage using some impressiveamazingacrobatics. When a girl is able to chase after a guy at full speed through heavy traffic and catch up to him, don't think she'll be one to give up her greater goals (becoming a full-fledged member of the Kaleido Stage troupe) so easily.
In Berserk, Guts is first seen having sex with a woman who turns into a demon, then shooting her with his arm cannon, then killing a bunch of thugs in a tavern with his crossbow and chopping one in half with one blow of his BFS. The purpose of this is to let the reader know just how ruthless Guts is, and to demonstrate his Badass qualities (although the sex scene in hindsight comes across as Early Installment Weirdness).
In the same episode, Yoko comes in swinging down on a rope and blasting the Gunmen with a sniper rifle. Then Simon falls on her, and she doesn't deliver the slap-in-the-face gut reaction you'd expect from a Gainax heroine.
Lelouch gets multiple of these in episode one. First, he turns around a nearly lost chess game by moving his king piece first, establishing himself as a brilliant tactician with a penchant for bold, audacious, and borderline reckless moves. Then, when Kallen crashes her truck, he is pretty much the only bystander who goes to help (while everyone else just stands around with their cellphones out and wonders where the ambulance is), establishing him as the one guy who will get his hands dirty to help a stranger. When he is trapped in said truck later, he deduces he is in Tokyo's old subway system by ear, showing his vast encyclopedic knowledge. This is often overlooked, but when he believes he's about to die, he thinks of his little sister—the one person he'd go to any length to protect. Finally, at the end of the episode, after using his Magical Eye to make the soldiers threatening him kill themselves, he flashes an Evil Grin, revealing just what kind of a fabulous Well-Intentioned Extremist he is about to start transforming into.
Suzaku is such a dynamic character that he gets multiple ECMs. His admittance to Kallen about killing his father, his willingness to use Nunnally to manipulate Lelouch, his Laughing Mad moment after the FLEIJA goes off. Exactly which moments properly establish his constantly evolving character is best left to personal opinion.
In Lelouch's flashbacks we see he is not physically fit when Suzaku beats him in a race up a hill as well.
When Cornelia is introduced, the very first thing we see her do is lead an army of elite Knightmare pilots to a stunning victory against clearly outmatched foes. The generic bad guys are blown to smithereens, and the viewer is treated to a visual of her Knightmare standing triumphantly over her fallen foes, surrounded by flames. At that point, it's quite obvious she's not to be trifled with.
Nunnally referring to Sayoko as Japanese and not Eleven.
In Nightmare of Nunnally, Alice is first introduced using her Super Speed powers to steal the skirts of the bullies harassing Nunnally. Later chapters reveal that this is not the first time she has done something like this.
Ryoma successfully prevents a Yakuza boss from stabbing him by grabbing his wrist in time...only to grip down on the blade with his free hand anyway, just to show how badass he is. "Come on, push or pull. You'll save face if you at least chop off a finger." This sets the tone for the rest of the series, which is mostly composed of Crazy Awesome and Slasher Smiles.
Ryouma: Walking into a multinational Martial Arts tournament, insulting everyone there, beating the shit out of everyone there, declaring that its revenge for the way the showboating modern martial artists had destroyed his father's career as a Dojo master, and then fighting off a hit-squad even after getting stabbed in the shoulder.
Professor Saotome: After Hiring above-mentioned hitsquad to test Ryouma's capabilities, his response can be summed up as such: "Good job, you proved you're a badass. Now shut up and get in the giant robot."
Hayato: Ripping a dude's face off with his bare hands for not being willing to follow him.
Azumanga Daioh opens in the manga with Yukari-sensei boisterously introducing herself...to the wrong class. The anime opens with her stealing a student's bike to get to class on time. Actually, Azumanga Daioh is very good at setting up what a character will be like on first meeting: Chiyo-chan tutors a very embarrassed older student in her second scene; Sakaki makes Chiyo nervous at first...and then we see her "preferred jobs" list includes "Veterinarian" and "Toy store clerk"; Tomo volunteers to stand in the hall with buckets and fails.
In The Prince of Tennis, Keigo Atobe, captain of the Hyoutei team, walks onto the tennis court for his match against Seigaku's Kunimitsu Tezuka amidst cheers and cries of "The winner will be Atobe! The loser will be Tezuka! The winner will be Hyoutei! The loser will be Seigaku!" from his large crowd of supporters. When he reaches the center of the court he raises his hand and snaps his fingers, silencing the crowd at "The winner..." He then flings off his jersey and exclaims "Will be me!" His supporters go nuts. And that tells you everything you need to know about him.
Our main character Ryoma Echizen establishes himself quickly in the first few scenes. First by telling off some bullies(mostly for being noisy), and then correcting them on their tennis grip.
Kamille Bidan quickly establishes just how hot headed he can be when he assaults an elite officer of the Federation just for making a crack about his name. This is the first of many rash actions he takes before maturing into a respectable man and soldier.
Domon Kasshustarts the first episode by befriending a kid, growling "Have you seen this man?" at a guy, and then cleaning up in a bar brawl. Allenby has one defining her as an Action Girl by pitting her in an arcade simulation battle against Domon. The machine broke down before either of them called it quits.
In Gundam Wing, the five Gundam Pilots each get their Establishing Character Moment in the first episode, where four of them get brief scenes showing their initial battles on Earth and parts of their personalities (Duo's enthusiasm and glibness, Trowa's cool head and stoicism, Quatre's nice guy with an edge, and Wu Fei being an Arrogant Kung-Fu Guy). Lead character Heero gets his at the very end when Relena invites him to her birthday party; in rapid succession, he tears up the invite, wipes away the tears that previous action caused, then whispers his Catch Phrase into her ear: "I'll kill you."
Mobile Suit Gundam AGE's Woolf Enneacle has an episode for this. He struts out of the shower declaring that he's the best and challenges Flit to a contest for the Gundam. Then in the second half, we see that his massive ego is actually justified because of his skills on the battlefield. The Hero of the second generation Asem is introduced when he beats up the bullies who are harrassing his friends and then worries about the mobile suit contest because he wants to impress his father. And third generation protagonist Kio proves his heroic credential by unhesitatingly staying in danger zone to rescue some left behind children amidst an attack on his home city.
Kodachi Kuno gets a very distinctive one as well, as when Ranma meets her for the first time, she's been cornered by three rival gymnasts attempting to get revenge on her for previous times she had ambushed them. Kodachi responds by feigning innocence, defeating them effortlessly, and then continuing to beat on them even whilst lecturing them on how "if I weren't a lady" she would really do something awful.
In the second episode and chapter of Chrono Crusade, Rosette gets hurt during a battle and is briefly knocked unconscious. Chrono then jumps to conclusions and assumes she's either badly injured or dead and has a Freak Out, trying to break the seal on his demonic powers on his own. In both versions it serves to establish Chrono's true nature as a demon, and also how fiercely protective he is of Rosette. In the manga it also establishes Chrono's Fatal Flaw—his temper—which pays off in volume 5, when he breaks his seal when confronted with Aion and tries to kill him—nearly killing Rosette with his powers and setting half of San Francisco on fire in the process.
After Kurt Godel's first appearance, it is quite clear that he is a manipulative asshole and a blatant liar ("Where have I seen your face? Couldn't possibly have been on Megalomesembria's Most Wanted...") — and that he is not one to be trifled with, politically or on the battlefield.
Firo's first appearance in the anime version of Baccano! has him taking out an old homeless man that was trying to stab him—even though Firo had given him money a moment earlier—after said homeless man cuts off a couple of Firo's fingers...which immediately reattach themselves.
The light novel introduces him this way, as well, except it replaces his fingers being cut off with him simply disarming his opponent and knocking him out (since at the point in the novel when he's introduced, he's still a Badass Normal).
Although it's not his first scene, Luck Gandor's establishing moment in the anime comes when he recites the first few lines of Edgar Allan Poe's poem "Spirits of the Dead," and reflects that where previously his fear of death made the poem terrifying to him, now that he is immortal he would no longer be afraid to die if he could.
The side story where Fuery finds a puppy in the rain is one for Hawkeye. She tells him to find the dog an owner by the end of the day, or he'll have to put the dog back. At the end of the day he tells her he couldn't find anyone - at which point she promptly adopts the dog herself. (At this point, Hawkeye was only a side character, and thus the reader believed she really would make him put the dog back in the rain.)
Izumi Curtis first appears as a bed-ridden woman. She then welcomes Edward by slamming her foot into his face. Then she happily greets Al. Then she judo-throws him. Then, as she's berating them for being out of shape, she suddenly spits a lot of blood. And finally she hugs her comforting husband in a lovey-dovey manner. There, that's (almost) everything you need to know about teacher Izumi.
Full Metal Panic! has Sagara Sousuke established right from his entrance to be an emotionlessBadass that doesn't have any particular feeling or compassion towards people dying. The whispered girl that he rescues asks him if he feels sad that one of his brave comrades died, to which he blankly replies that he doesn't really know or feel anything particular.
Gauron's establishing moment during the first episode he's shown...where he has shady dealings and smugglings with the KGB. When the huge, muscled lieutenant gets angry at him for raising his rates, calling him a "Chinaman" and threatening to throw him into the labor mines, Gauron calmly and smilingly takes out his gun and pumps the man's head full of lead. He then proceeds to happily go up to the terrified colonel and continue discussing business. It certainly sets the idea and tone for the rest of the story that Gauron is a complete Ax-Crazy psychopath that won't hesitate to kill anyone for the heck of it.
Balalaika gets one of these at the end of the third episode of Black Lagoon, when she calls the Lagoon Company in order to tell them a "very funny joke," the punch line of which is her firebombing the apartment of that arc's antagonist. While there were a couple of hint in the two previous episodes, this scene is the moment that clearly establishes her as the Affably EvilSociopathic HeroBlood Knight that she is.
The first episode has a number of examples: Dutch with his cool-and-in-control persona as he competently manages a group of hostages. Revy's establishing moment during the next scene shows her as a psychotic woman with a Hair-Trigger Temper, and caps off with Revy trying to shoot Rock while looking away before being corralled by Dutch, the only person on the crew who can handle her. Rock is initially portrayed as a quite fearful Fish out of Water, but in the Yellow Flag scene, the first clue we're shown that he is more than he seems is when he drains his rum in one gulp before Revy's shocked eyes, leading to a drink-off between the two. And then the shootout, which shows Revy sporting a Slasher Smile while capping a group of hardened mercs with Guns Akimbo, establishing just why she's called "Two Hands."
Benny also gets one when he comforts Rock in a later episode regarding the fates of Hansel and Gretel, showing that while he's a nice guy, he's utterly desensitized to the violence.
Chaka's first appearance has him cursing out his girlfriend over the phone during an important meeting then trying to pick a fight with Revy by beating up Rock. Combined with his sloppy purple suit, unkempt beard, and long bleached hair (compared to the others' grey or black suits and clean cut appearance), viewers have everything they need to know he's an unprofessional delinquent who thinks he's hot shit.
Aside from kicking ass (in most cases, anyway), the Suzaku and Seiryuu Seishi from Fushigi Yuugi commonly make an entrance while their body symbols are glowing.
The anime of Trigun pulls this off beautifully with its main character, Vash the Stampede. His very first first appearance, where he survives a saloon being blown to pieces, belies his later appearances as an incompetent goofball, giving the audience brief but profound proof that, despite his immature behavior, he really could be the legendary outlaw.
Shinji Ikari - an introvert concealing large amounts of rage at his father over being abandoned yet still returning when his father calls, and then submitting to his father's manipulation of protecting others while putting himself at risk both physically and emotionally. An amazingly complex character, but all pretty well established in the first episode.
Misato Katsuragi - Wild party girl in her picture, drives like crazy, sympathetic in a motherly or Cool Big Sis way towards our hero, established in the first episode.
Gendo Ikari - a cold hearted bastard who manipulates everyone, and willingly sends his own child into mortal combat and attempts to send a heavily injured Rei when said child refused, first episode.
Rei Ayanami - mysterious, magical, stoic, obedient, all in the first episode with only a single line of dialogue.
Asuka Langley Sohryu - the infamous introduction, following her skirt blowing in the air: *SMACK* *SMACK* *SMACK* "What was that for?" "Viewing fee."
That's only half of her character, though. In the next episode, she is shown crying in her sleep about the loss of her mother, which displays her sweeter, almost completely hidden side.
Kaji - "Is she still wild in bed?" While playing footsie under the table. Oh Kaji you Handsome Lech you.
Shortly afterward, we get Asuka's introduction, which is much more...er, theatrical than her series one.
Theatrical meaning she leaps from a plane in a giant robot, and tears one of the largest Angels shown so far a new one before she ever touches the ground. It was dead by the time she landed.
From the Yu-Gi-Oh! manga, the very first image of Yami No Yuugi, or the Pharoh, has him dressed in leather, casually perched on a brick wall, and giving a bully, who had beaten the crap out of his host hours before, what can really only be described as the mutant offspring of a Rape Face and a Death glare. Within the next few pages, he challenges the bully to a game that consists of nearly stabbing their hands with a huge hunting knife through a stack of dollar bills. The bully loses. The Pharoh does something to convince the bully a pile of leaves is really a pile of cash. It's implied that the Bully never recovers from this. You now know everything there is to know about the Pharoh.
Gunslinger Girl first shows Henrietta, the quiet little girl with a violin case, break a mans' neck with said violin case, before opening fire up on a group of thugs with a P90 submachine gun...''remaining completely expressionless.'' It quickly switches to a montage of her training, which she tackles in the same emotionless, mechanical fashion. The next scene, though, has her puddling up when her handler admonishes her for being reckless, effectively demonstrating that for all the killing, she's still a little girl.
In the first episode featuring Triela we see her acting as a Cool Big Sis to Henrietta, then it changes to her running down a Mafia mook who she takes down with a few aimed blows, then shoots without orders when he draws a gun, then she backchats her handler over the matter when he reprimands her — all establishing Triela as a kind, mature, skilled Action Girl with a touch of independence and rebelliousness unusual in these brainwashed cyborg killers.
K-On! has the main character Yui oversleep, almost drop her cell phone in an attempt to pick it up, panic, race to school, (falling over on the way out), saying goodbye though a mouthful of food. Even in her rush to get to school on time, she doesn't neglect to pat an adorable puppy and help an old lady across the street..... and when she does get there, she finds out that she got there early by mistake, having read the clock wrong.
Spice and Wolf does a great job with Horo, who, first and foremost, howls. Then she asks for some ale, grabs some food, messes with Lawrence's head, plays with his emotions a bit, announces she'll be traveling with him, and then goes back to sleep, in about three minutes flat. A second moment shows a more fragile side, as Horo reflects on how she's no longer needed by the people she had watched over.
And in the very next scene, Celty gets hers: "The world isn't as cruel as you make it out to be."
In the light novel and the manga, Izaya manages to do this to two girls at the same time. Oh, he also drugs them and stuffs them into suitcases. Then he stands on a rooftop and laughs like an absolute lunatic while declaring his love for humanity. He's also the most popular character in the series, natch.
Also from Dragon Ball, Chi Chi is being chased by a T-Rex. While crying and running she removed a boomerang from her helmet, throws it, and decapitated the T-Rex. When she realized what she had done she vaporize the body with a laser built into her helmet.
The very first moment of Omega Shenron from Dragon Ball GT involves him killing his own fellow Shadow Dragon for actually sticking to an honor code.
Actually he was aiming for Goku but Nuova Shenron jumped in front of the blast. It was never his intention for Nuova Shenron to die.
Pan's fight with the bank robbers manages to condense her cockiness, compassion (trying to get the person she though was a little kid out of there), ability to fight and bravery (remember, she's supposed to be 10, and is already at least stronger than Android 20 (Dr. Gero).
The Wandering Son anime adaptation has Chiba smacking a boy with a book on the head when he taunts Nitori, the object of her affections, about if he and his platonic life partner dated. At that period in time Chiba had a disliking that person, and she walked out of the classroom after attacking him. This scene shows off her Violently Protective Girl Friend and Clingy Jealous Girl behavior. A different variation happens in the manga where she's introduced asking Nitori if he was involved with a girl, to which he replies no. This makes her happy and she leaves, which makes Nitori monologue about how she's strange; this scene sets the mood for her social awkwardness.
The manga is pretty good at this. Chizuru is introduced in both medias as wearing the male uniform on the first day of school, and later essentially hitting a girl; this shows off her calm Cloudcuckoolander nature and her Genki Girl attitude. Her best friend Momoko is first seen clingy at her side, Oka is first seen asking Nitori if he has any masculine interests before dismissing him, Yuki is first seen seemingly flirting with a ten year old..
The first sight the audience gets of Kotetsu in Tiger & Bunny is him standing on the rail in his Wild Tiger costume, waiting to intercept a hijacked monorail. When the producer of HeroTV instructs him to wait until after the commercial break to make his move, he refuses, telling us more or less everything we need to know about his role in the series.
Barnaby gets a positive one when he saves Kaede (though he had no idea she was Kotetsu's daughter) from certain death — it's the first indication that despite his apparent coldness and indifference, he's not heartless.
Hei of Darker Than Black is introduced viciously interrogating and then killing a Contractor, showing that he's not at all a typical hero. He then gets a very different establishing scene in his civilian identity as Li, where he's a nice, gentle guy. The series is all about reconciling the two moments.
Haku's first action in Spirited Away was to tell Chihiro to leave the spirit world for her own safety and distracting the other spirits, despite (seemingly) not knowing her. Later, when he gave her some food to stop her from disappearing, he lets her touch his hand to prove that it worked. It was a quick blink-and-you'll-miss-it moment but Haku's tender expression towards Chihiro proves that he isn't as cold as he seems.
Tsukasa walking in on Kagami and Miyuki while still in her pajamas.
In Mai Hime, Shiho is first established as a Clingy Jealous Girl when she punches Yuuichi out of the way when he tries to give Mikoto CPR, saying that "(his) eyes look indecent".
Haruka's first scene has her yelling at Mai for the property damage caused by her arrival at Fuuka Academy, while the other student council members are calmer and more welcoming of Mai.
Rurouni Kenshin: Kenshin's first act is to dodge Kaoru's attack easily, then feign Obfuscating Stupidity after realizing she's not a threat. His first mission statement, in the same chapter, is to state that while "the sword that protects life" is a foolish ideal, he prefers it over the reality that is the killing art of swordsmanship.
Sanosuke is introduced as a restless figther who almost seems like a typical bully in his thirst for fights. His subsequent appearance in the Akabeko then establish him as more of a heroic if cynical figure after he beats up some noisy drunks. He also shows how observant he is with Kenshin's Obfuscating Stupidity.
Saitou Hajime takes at least two to establish himself. In his debut, he shows off just how deadly he is by effortlessly defeating Sanosuke. Once his true colors are revealed, he tells his former employers that though they can bribe and tame anyone else, he only operates on his own code.
In the very first scene of Bakuman。, Moritaka Mashiro is sitting in class, bored and pessimistic about his prospects if he gets a "normal" job while drawing a detailed sketch of his crush Miho Azuki.
Akito Takagi appears in the classroom holding Mashiro's notebook. Instead of making fun of him or blackmailing him, he simply asks Mashiro if he wants to make a manga series with him, showcasing himself as a guy with big ambitions.
Eiji Nizuma's first mention is when he wins an honorable mention in a manga contest, and says that he won because he was drawing while other kids his age played video games. This comes off as somewhat arrogant to Mashiro and Takagi, but it also shows the depths of Eiji's passion for manga, especially when Eiji later confirms that he had to draw because he didn't live near others and his family couldn't afford video games.
The editor in chief, in response to Eiji asking to cancel one series he doesn't like if he becomes the top-ranked manga artist, says he will consider the request if he still wants to do it after he learns about the difficulty of becoming a professional and becomes the top-ranked manga artist, showing his respect for determination.
Bleach gives us Kurosaki Ichigo who is seen beating up a bunch of thugs because they knocked over a vase which was an offering to a little girl who died recently. It would turn out Ichigo was doing all of this for the little girl, who came back as a ghost. He later tells the ghost girl that he will bring her new flowers and to hurry up and go to heaven.
Ginjou was introduced by bumping into Ichigo and acting like a spaz as his bag was dropped. But as soon as Ichigo hands the bag to him and leaves, he flashes a smirk and his face was framed in shadow.
Nanao finds Kyoraku sleeping and tells him intruders have broken into Seireitei. He lazily responds with "What do you want me to do about it?" This was significant for another reason because Kyoraku's Evil Counterpart Starrk has the exact same exchange with Lilinette during the Hueco Mundo arc.
Gin's first appearance involves him slicing off Jidanbo's arm and declaring that for a gatekeeper, losing means death. He then stays around long enough to confirm Ichigo's identity, then starts to walk away, only casually knocking Ichigo back and forcing the gate shut when Ichigo plans on fighting him.
Chad's first scene in the manga has him catch a steel bar before it can hit the parakeet his friends just gave him, shrugging off any damage.
Aizen gets one as well, but not when we first see him. In fact: his moment comes when he stabs Momo after revealing he's alive, and effectively saying in his calm tone that he really didn't care what he just did to her. The rest of the Soul Society arc forever establishes him as the main villain and Big Bad.
One of the Zero Squad members gets hers by way of Mayuri - she reveals that she broke into his lab and then calls him out for his lack of security. He sits there and takes it. Considering we know that a) Mayuri hates having his lab messed with and b) is rather lacking in sanity, that he'd react in such a way nicely highlights what kind of badass we're dealing with.
Mayuri himself gets his when, after his human bombs that he sicced on Uryu fail, blows them up anyway. "A bomb isn't supposed to come back."
Harima monologuing about the wonder of love after he had just beaten the tar out of a bunch of delinquents.
Harima and Hanai try to impress their boss with their strength while working part-time as movers. The boss says they're not as strong as "Ichi-san" who they picture is a big burly dude. Turns out she's a tiny girlwho can lift a piano.
Tomas reads aloud a letter from an MLS agent to his wife, which Tomas stole after killing the man, and derisively refers to it as drivel. This nicely establishes how he's one of the nastier antagonists, who makes Goryo seem like a decent human being in comparison.
How does Sengoku Basara introduce us to SanadaYukimura? Oh, just by having him blow open a giant door with his Dual Wielding spears, making a dramatic speech while whooping some Mooks, and eventually summoning a spiraling tornado of fire to impress his badass mentor!
Axis Powers Hetalia has several of these in the first chapter. America shows his Man Child personality and how they can make a huge hero to defend the earth. Switzerland irritably snaps at Japan for agreeing with America. England first appears to be the Only Sane Man (with a hint of Tsundere towards America), only to lose his temper when France speaks up and then get into a fight with him.
Then China attempts to calm things down but is ignored. Greece shows his philosophical side while being surrounded by cats and later is seen sleeping when the rest of the countries argue amongst themselves. Russia mentions enjoying seeing Lithuania begging to him in tears with a cheerful smile and then asks if Latvia agrees (while Belarus holds a knife to his throat). Poland jumps in to protect Lithuania from Russia. Germany yells at everyone to shut up and strictly proceeds on with business. Italy, when chosen to speak first, shouts out his trademark food "PASTA!!!!!!!!!!!"
Italy gets another one when he first meets Germany; he's found hiding in a tomato crate, tries and fails to convince Germany he's a fairy, then tearfully surrenders and begs for his life.
In Canada's first appearance, he apologizes for being late ... with no one realizing who he is.
Naruto's introduction establishes his nature as a prankster well enough, but the first scene that shows how there's more to him than that is when he sits on the swing, looking on at all the other kids who graduated get congratulations from their parents, while he is the only one who failed, showing the depths of his loneliness and isolation.
In Iruka’s second scene, he tells Naruto that he can’t go home until he cleans the monuments, and Naruto sullenly responds that he has no one to go home to. Iruka ponders it for a moment, then tells Naruto that if he finishes, they’ll go out for ramen, effectively showing that Iruka may be strict, but also cares for Naruto.
Gaara’s pre-Heel–Face Turn character is established when he breaks up the fight between Kankuro and Team 7 by threatening to kill Kankuro, his own brother.
Then episode 34 comes by... Hoo boy! He kills three people who he claims looked at him the wrong way, wants to kill Team 8 and threatens to kill his own SIBLINGS when they try to reason with him! Good grief! And he only gets worse before he gets better thanks to Naruto!
Might Guy appears in a puff of smoke, brags about his rivalry with Kakashi, punches Lee for using the Primary Lotus in a sparring match, then tearfully hugs him and assigns him laps.
Jiraiya is introduced peeping on women in the baths, then knocks out Special Jonin Ebisu with one attack.
Sai is introduced kneeling before Danzo, with a smile Danzo knows is fake. When told to stop it, Sai apologizes, saying that he read smiles are good for such situations.
Hidan and Kakuzu's introduction indicates their conflicting personalities as a psychotic religious zealot and a practical, greedy mercenary. Hidan confesses that he might kill the Two-Tailed Beast's host in a rage, prompting Kakuzu to remind him that the mission is everything, to which he responds that his religion forbids not killing opponents.
Suigetsu, shortly after being released from his tank, complains about the other two members Sasuke is planning on recruiting for what he then calls Team Snake. He then tells Sasuke that he isn't necessarily any better than the others who tried to take down Orochimaru- he only had more opportunities- while making threatening gestures at him, before backing down when Sasuke is unfazed, signifying that Suigetsu is not much of a team player.
A is lifting a barbell one-handed while being told that Killer Bee has been captured. He then smashes his desk in anger, vowing to go after his little brother.
In Mai-Otome, Nina's introduction involves her getting a drink as a gift from some admirers among the passengers of the sand ship. A desperately thirsty Arika then runs into her, spilling part of the drink on her and gulping down what's left, resulting in her adoptive father getting a look at her panties and her being mortified.
Shiho tells some Corals gossiping about Nina possibly facing expulsion for the incident in Episode 1 that they shouldn't talk about their classmate like that. When they're out of earshot, she gleefully holds up her "spiraling" stick and declares that this is Nina's punishment for not accepting her offer to be her room attendant.
Detective Conan has Teen Genius Shinichi solving a case and cannot resist the challenge. He meets up with his childhood friend Ran, who after he casually insults her father, punches a metal pole while cheerfully smiling.
In Sailor Moon, the episode that debuted Makoto Kino had her effortlessly beating up three punks who were about to assault Usagi for running into them. This is her very first scene, and well before she even knew she was Sailor Jupiter, and before she even knew who Usagi was.
Codename: Sailor V establishes Minako as not your typical Magical Girl and a Bunny-Ears Lawyer when her mascotte Artemis shows up to tell her she's a Magical Girl and she kicks him out of the bathroom while calling him a pervert, then leaves wondering since when cats can talk.
Usagi's first scene is her sleeping in late, nearly forgetting her lunch, and running to school while still half asleep. That's it. That's all you need to know about Usagi.
Koichi Shidou of Highschool of the Dead first appears to be a well meaning teacher concerned for the safety of his students. But when one of said students breaks his ankle and pleads for help, Shidou responds "Oh well, that's it for you!" and stomps him on the face before casually walking away and leaving the boy as zombie food. What a dick!
Fairy Tail gives a pretty unique one to its main villain, Zeref. After building him up for 200 chapters as the ultimate evil the readers are shown a scene of him (though he goes unnamed at the time) about to be attacked by a pack of wolves. After killing them without trying he apologizes for having taken their lives, and in fact tried to ward them off before they could attack so that they'd remain unharmed. It was such a drastic difference from what readers expected that despite earning the nickname "killing mage" virtually no one considered he may have been the anticipated villain.
In the scene where Fairy Tail guild master Makarov is introduced, he scolds the members for the huge number of complaints regarding their reckless behaviour that he has received from the council, and immediately proceeds to burn away all those complaint letters and tells the members not to care about the council. Said scene also serves as one for the respective members, establishing some of their quirks- Cana's drinking habit, Loke's womanizing, Gray's stripping and Elfman's obsession with manliness.
The first chapter/episode showcases Natsu and Lucy quite well. Lucy seems to be an average fan girl but shows courage in confronting the villain of the episode with her stellar spirits. Natsu shows off his many Idiot Hero traits before revealing his true power as "Salamander".
Brandish Mu of the Spriggan 12 is introduced complaining about how the fight between Marin, one of her subordinates, and the Fairy Tail wizards, resulted in the destruction of a food stand she wanted to visit. When Marin complains and insists that she help take care of the Fairy Tail mages, she shrinks him (someone who'd previously been at an advantage against the entire group) and the entire island, showing that she has her quirks, but she's not to be trifled with.
The first episode shows off Spike's badassery as a martial artist practioner and experienced bounty hunter, before revealing his bullheaded destructive tendencies in his conversation with Jet.
Panty & Stocking with Garterbelt: When the two girls are first called into duty, we see Panty sleeping with a man who had been in her bed; establishing her as a village bicycle. Stocking is eating a piece of cake, establishing her love of sweet foods. These become the catalysts of their behavior for the rest of the show.
Soul Eater: The first trio of episodes has these for the main characters, while also establishing the main flaws in the partnerships:
Maka and Soul Eater are introduced fighting and defeating a kishin egg, demonstrating they're capable students. Only afterwards do they start arguing.
Death the Kid enters the story apparently having no trouble hunting down a monster he's cornered in an alley. Then he's distracted by his partners slightly inaccurate "Super Sentai" Stance...and gets so upset he fails to notice his target is running away.
Mako Reizei is first seen staggering to school, complaining about how painful mornings are. When she arrives, she's met with a Disciplinary committee member who says she's been late over 200 times, and for whom she has a nickname of her own.
The first thing ErikaItsumi says to Miho is "Vice captain... Ah, I mean, former vice captain" in a highly sarcastic and patronizing tone of voice. As she's leaving, she says Oarai is going to lose the tournament, with it only being a question of how badly, and it should not even be entering in the first place.
Maho's moment comes in Episode 6 when she tells Erika to fly Mako to the hospital so she can see her grandmother, and justifies her decision by saying that doing so is also part of tankery. This not only shows her kinder side, but also her belief that adherence to a Serious Business ideology of tankery and acts of kindness are not mutually exclusive, especially not when she is motivated to live up to the expectations for her as Nishizumi Heir out of a desire to allow Miho to live and do tankery her own way.
Miho and Maho's mother Shiho is first shown berating Miho for abandoning the flag tank to save the crew of another, telling her that she's expected to live up to the family standards, and that it's impossible to win without sacrifice.
Nonna's second line of dialogue has her telling the short-tempered Katyusha to wipe her face, indicating her motherly behavior towards Katyusha, and her being close enough to Katyusha to be able to correct her.
In Little Army, Miho's tank crew gets establishing moments in rapid succession after their class gets news that Miho's older sister, an alumna of their elementary school, won a tankery tournament. Hitomi runs over to Miho, falls on her face and asks to become one of Miho's sister's fans. Chihiro apologizes to Miho for Hitomi's eager questioning. Emi is the only one in the class who is openly displeased at the fact that Maho won the tournament, and by commenting on the strength of German tanks, reveals her knowledge about tanks not only to the viewer, but also to Miho.
Tokiwa from Ask Dr. Rin! first appears at the end of episode 1, staring at a photo of Meirin with Asuka's face scribbled out. Guess who he spends the next few episodes trying to win the affections of and who he spends the next few episodes trying to murder? This is subverted later, however. It's a good Character Establishing Moment for the first few episodes, while he's possessed by a demon, alone. Once the demon's been exorcised, he becomes much nicer, more like Vitriolic Best Buds with Asuka, though he still has affections for Meirin.
In Space Battleship Yamato 2199, ErichDomel's first scene has him inflicting a Curb-Stomp Battle on the Comet Empire, warning one of his subordinates to never underestimate the enemy and then telling him to finish destroying the enemy ships, talking with another on how this last victory should rid them of the Comet Empire for a while, and protesting being recalled home to get decorated and promoted because he has a job to do until the commander in chief tells him that Dessler has a problem he needs Domel to take care of.
In Saki, Mihoko, after winning the first round of the prefecturals along with the Kazekoshi team, prevents her coach from slapping her close friend and teammate Kana for making a minor mistake late in her match, telling her that Kana is skilled and that if she makes any mistakes, she will take responsibility. After the coach storms off, Mihoko hugs and comforts Kana, showing her motherly and protective relationship with the Kazekoshi team.
In Achiga-Hen, Toki and Ryuuka's first scene involves Toki falling to her knees, prompting the Achiga girls to rush over to help her, only for her close friend Ryuuka to leap to her side from even farther away.
Yuu's first scene shows her under a kotatsu in the middle of summer. She's shy enough to be startled by her sister bringing along two guests, one of whom she knows. After she gets over that and her initial shock at her sister telling her that they're reforming the Achiga girls' mahjong club, she says she's happy, as she always wanted to be in the same club as her sister but didn't feel as though she could join.
Amelia, the chef of The Voynich Hotel attempts to commit suicide, fails, and tries to poison a hotel guest so she won't die alone. When Elena foils her murder attempt, she quietly goes back to work. This is pretty much her entire life. And it is hilarious.
The first action of Eren's Titan form is to deliver a massive punch to a Titan about to eat Mikasa, then proceed to stomp its neck to death.
The Beast Titan's first order of business is to casually terrify Mike Zakarius, one of the most powerful members of the Survey Corps, before ordering a group of Titans to tear him apart.
Hell, the simple fact that it can talk is a pretty big indicator of his character.
The first three episodes of HeartCatch Pretty Cure! essentially establish that, unlike the previous Pink-type leaders and their Blue-type best friends, Tsubomi Hanasaki was a very timid and shy girl and that Erika Kurumi was the Genki Girl of the series. The opening scene of episode 2 also showed that Tsubomi had a long way to go before she could be established as a respectable Cure.
The very first scenes of the manga show a purple haired girl onstage making a grand speech. In a few panels, she states her grand purpose to help the student body with all their problems using only a suggestion box. Thus we are introduced to our titular character Medaka Kuromkami, our ambitious all-loving heroine
Zenkichi takes a few scenes to establish his character. Among all the students, he's the one who claims cynically that she's only "standing over everyone". Yet this same student is the childhood friend of Medaka and at the start of the series the only one who talks to her normally.
Shiranui appears to be just a goofy friend of Zenkichi. But during one conversation she chides Zenkichi on misinterpreting Medaka's motives, showing there's more to her than it seems
Kumagawa Misogi has perhaps the most unsettling introduction in the series. While there were certainly a few earlier scenes discussing his character, his actual debut comes right after the protagonists have finished taking on the Flask Plan. What do they see? Twelve bloodied fighters pinned to the walls with screws. Out comes an unassuming boy who proclaims "It wasn't my fault".
Hachiman Hikigaya's first monologue establishes just how jaded and spiteful he is regarding High School life. But his later speech regarding "hard work providing consolation" shows he's not as hopeless as he seems.
Hiratsuka's first scenes include exasperatedly insulting Hachiman, nearly punching him, before finally deciding to put him in the service club.
Yukino Yukinoshita seems to be your typical bookish regal girl, until she launches into her brutal snarkfest upon seeing Hachiman.
Basara first runs into Mio while she's using the bathroom. He then ends up going inside and covers her mouth up to keep her quiet, lest she screams and someone mistakes it for an assault.
When Yuki is first introduced in episode 2, the first thing she does is give Basara a hug. This angers Mio, as well as the rest of the boys at his school due to the two girls being viewed as untouchable idols.
In Cute High Earth Defense Club LOVE!, Yumoto manages to chase after a wombat in a hot spring bathhouse when he would normally slip. En and Atsushi were talking about oden ingredients when the wombat arrived and talked to them about saving the world with love. Not only does that set the roles for 4 characters, it also tells the viewer they're in for one heck of a Parody.
Fate/Zero establishes each of the Masters within their first scene.
Kiritsugu's first words to his wife after she had just given birth to their daughter is how he will kill her. She's totally fine with it.
Kotomine's father, along with Tokiomi, instructs Kotomine about how he will help Tokiomi use the Grail for their own gain despite telling Tokiomi that their role as priests is to keep the Grail War as unbiased as possible. Afterwards, the father tells Tokiomi about how depressed Kotomine is over his wife and how he hopes the war will help him.
Kayneth berates a student over his paper about how training can make a mage better than a mage with a powerful lineage. Pissed off, said student steals Kayneth's package and enters the war to prove himself.
Kariya marching towards his father's house after learning he essentially took one of the daughters of The One That Got Away to create a Magus and asking to fight in order to spare her.
And lastly, Ryunosuke murdering a family and carelessly asking a kid if it's okay that a monster comes and eats him.
In Yona of the Dawn, Shin-Ah's first act was to rescue Yona, a stranger at the time, from a kidnapper and gently lead her back to her friends.
Joseph Joestar is introduced rescuing the guy who pickpocketed him from Corrupt Cops, punching out one's face for insulting him and disarming the other with a trick using his Hamon and a bottlecap. All that while he may have the come core morals as his grandfather, he's not gonna be the same person.
Josuke is introduced trying to get over his fear of turtles and letting a bunch of delinquents step all over him, even after they injure the turtle he was trying to touch. Then their leader makes the mistake of insulting hishaircut, whereupon calls out his Stand and uses it to literally rearrange his face and heal the turtle.
In Re-Kan!, Narumi first sees Hibiki at a crosswalk. The latter crosses the street by hopping up and down and screaming. Narumi thinks she's strange at first, until she spots some handprints on Hibiki's leg, and then sees a ghost boy clinging onto it.
Daryun is a skilled fighter loyal to Arslan when he deliberately misses his shot at killing the boy who kidnapped the prince at Arslan's plead.
King Andragoras furiously demotes Daryun at his suggestion that there is a trap and they should reconsider blindly charging at the enemy, thinking it was a coward's way out. He also harshly calls out his son Arslan for arriving at the scene when he wasn't summoned.
Gieve mercy-killed a captured general who begged to be killed by an ally than tortured to death by Lusitanian soldiers, shooting an extremely faraway distance to fulfill the general's wish.
Hijikata of Peacemaker Kurogane stepped in to stop Okita's deadly attack on Tetsu with his bare arm, breaking the wooden sword in half instead.
Okita initially appears as a delicate, girly looking boy but as Tetsu and Tatsu finds out, he is actually one of the best and frightening swordsmen of the Shinsengumi.
And then there's the suicide bomber, Nagisa. He executes the plan by first going up and trying to stab Korosensei first, and then when he blocks, he hugs Korosensei with a grenade around his neck. This foreshadows his talent for assassination, his lack of self-esteem, and his eventual modus operandi when executing an assassination.
Rider, a tall, elegant magical being, is summoned into the mortal world with much pomp and ceremony...and she immediately turns away from her summoner to examine the hurt, naked girl collapsed on the floor. Later she asks the girl's name, despite Shinji's insistence that she is worthless and irrelevant to Rider's duty.
Taiga, a grown woman, takes childlike glee in pranking Shirou by switching the house's sauce bottles.
Rin "wasting", in her words, a stockpile of powerful magic (that was a gift from her father, no less) to save the life of an innocent caught in the crossfire of the Holy Grail War. Heart of gold, that girl.
In the framing story of Despair, Chisa watches a film of herself being brutally murdered and idly comments on it while eating popcorn. Then she excitedly realizes that it's just like an scene in one of her favorite movies. ChisaYukizome, everybody.
In Future, Munakata deliberately arrives late to a meeting between Foundation leaders as a way of showing disdain for their commander, and coldly orders the squabbling leaders to act more professional.
Sakakura beats up a handcuffed man who's been accused of treason (not proven to have committed it) and has to be called off by other people.
In Bokurano, Masaru "Kodama" Kodaka's introduced using a sparkler to burn a crab to death, and when he's called out on it, he replies that it's no different from how humans eat meat. This shows he's not only capable of acts of great cruelty, but also of rationalizing said cruelty.
Izuku in My Hero Academia is introduced as a child defending another young boy from some bullies, despite being Quirkless, hopelessly outmatched and terrified.