Baki the Grappler has several: Doppo Orochi, Gouki Shibukawa, Kaku Kaioh and Ryu Kaioh...and not one of them stands a chance against Yujiro.
Kaze Gorou from Bartender was the undisputed master of Tokyo's cocktail bars, and proves to not have lost anything, even with age and the after-effects of a severe stroke taking their toll. Ryu's sempai Kitagata has the skills, gives off the "seen-it-all" vibe and has the world-weary attitude and disrespect for the "young whippersnappers" of an Old Master, but is in his mid-thirties at the oldest.
Bleach: Yamamoto has been the captain-commander for a thousand years because no one in that time has been strong enough to challenge his position. He is enormously powerful. His Zanpakutou is the most powerful offensive sword in history but when it's taken away from him, all he does is show case his mastery in all the other Shinigami Arts as well, displaying insane punching speed and strength, extremely fast Flash Step movement, and Kidou battle spells so powerful that they're matched solely by the specialist Kidou Captain and Aizen. He founded the training academy and his best students were Captains Kyouraku and Ukitake, whom he regards as being like sons to him.
In Demon Slayer: Kimetsu no Yaiba, there's a figure of legend who got this close to killing the originator of all demons, a demon slayer samurai who kept his humanity but had skills that practically made him inhumanly strong, almost divine in nature; it turns out he managed to live for 80 years and in his final moments still wanted to dispatch his older twin brother who became a demon, his brother notes than even as an 80 years old man his skills still seemed absurd, something that made a demon who kept his youth feel envious.
The Muten Roshi (which means "Heavenly Martial Arts Elderly Master"), who is the founder of the Turtle Style School and the inventor of the Kamehameha. While he's long since been surpassed in sheer strength by his pupils, Dragon Ball Super proves that he is still an incredibly skilled fighter when he takes part in the Tournament of Power (featuring 80 of the best warriors from eight different universes), and takes down three fighters entirely on his own. Goku even marvels at how his teacher has only become stronger while the rest of the Dragon Team weren't looking. In the manga version, the Muten Roshi even holds his own against World's Strongest Man Jiren the Grey with his own incomplete form of Ultra Instinct, explicitly thanks to his century’s worth of martial arts experience.
His former friend turned rival, the Crane Hermit of the Crane Style School, is this as well, due to the fact both of them are over 300 years old.
Makarov Dreyar. 88 years old (actually 96, thanks to spending seven years frozen in time), incredibly powerful, and master of several different types of magic, on top of being one of the ten Wizard Saints. That title is only granted to the most powerful wizards in the land, and it's implied a few times that Makarov is one of strongest of all of them.
Warrod Seeken. Over 105 years old and even stronger than Makarov, being one of the Four Gods of Ishgal (the strongest members of the Ten Wizard Saints and all of which are said to not even be fully human anymore) and one of Fairy Tails' original founders. He was also one of Zeref's students with Hades below.
And on that note, Precht"Hades"Gaebolg, another of Fairy Tail's original founders, the Second Guild Master, and current Master of the Dark Guild Grimoire Heart. Also over a hundred years old and strong enough to toss the aforementioned Makarov's Titan form around like a ragdoll, fight Team Natsu without much difficulty, and was the most powerful villain after Big Bad Zeref to appear in the series Pre-Timeskip and still a contender after it to the other ArcVillains.
Ryuken in Fist of the North Star, the previous Hokuto Shin-Ken master who trained Kenshiro and his adopted brothers. Also, Ryuken's old rival for the succession, Koryu, as well as the Hokuto Ryu-Ken master Jukei, both qualify.
In his prime, the Hero Himmel from Frieren: Beyond Journey's End was a veritable Master Swordsman who led the party that slew the demon king despite being rejected by the Hero's Blade. In his old age, shrunken and alone, he was still able to kill demons like its nothing as a soldier traveling to the Goddess' monument recounts to Frieren and co.
Henkyou no Roukishi Bard Loen: Despite the old age, Bard is more worried about overcooking the fish than the assassin in front of him. While he thinks The Undefeated Knight is an exagerrated nickname, he lives up to it by beating a dozen of armored guards with bare hands.
Netero, who was still one of the most powerful people on the planet despite being over 110 years old. Not a sensei anymore, and still active (though rarely involved in fights) as the head of the Hunter Association prior to his death, but he fits the trope otherwise.
Biscuit Krueger is a subversion, as she's in her late 50s but uses her powers to resemble a young girl, and even in her true form she doesn't look older than mid-30. She was a master of Nen as well as Netero's style of kung-fu, and trained Gon & Killua throughout the Greed Island and Chimera Ant arcs.
Jiji from Ichi the Killer wears baggy clothing and walks with a slump in order to disguise his true strength.
The first words out of anyone's mouth when they face down Andrei Rublev on IGPX: Immortal Grand Prix's race tracks tend to be something like "The game's changed while you were away, old man!" The next words, usually said a few minutes later, tend to be something like "Man! The Rocket's no joke!" while their mechs are either flat on the track or in some other pants-down situation. However, Andrei is a downplayed version. While his tactics still leave pilots reeling, his body can't keep up nearly as well as it used to: the years between his retirement and his temporary comeback were not kind to him.
Hayato Furinji of Kenichi: The Mightiest Disciple. He is the undisputed most experienced and powerful master in a series filled to the brim with martial arts masters. Unlike many other Old Masters, though, Hayato still has an imposing physique: the man is huge and extremely buff despite his advanced age.
Prince Kamehame, despite being 70 years old and having a bum heel, is able to defeat Kinnikuman via pinfall in only seven seconds. In the Dream Choujin Tag Arc, he wrestles alongside Kinnikuman in his Kinnikuman Great guise, and they defeat Black Hole and Pentagon together before he's mortally injured by Sunshine's Cursed Roller.
The original head trainer in the Space-Time Administration Bureau from Lyrical Nanoha, an old woman who the supplementary manga reveals had trained Nanoha and Fate. And just to make a point on how much more the two leads need to learn despite the events of the first two seasons, she, a lowly AA-ranked mage using standard equipment, managed to beat the two of them at the same time.
Mobile Fighter G Gundam: Master Asia's not as old as he looks note Apparently the Incurable Cough of Death somehow makes him look older than his actual age of 50. but he is still past his prime and the Grand Master of the School of the Undefeated of the East. He can effortlessly catch cannonballs and demolish Humongous Mecha with his bare hands, and when putting forth some actual effort can punch a skyscraper hard enough to launch it into the air. While G Gundam is a World of Badass, virtually no one else is that badass. In fact, he's so badass that his use of the Master Gundam is him basically handicapping himself.note His real Gundam is an unseen one called the King of Hearts, but he never uses it because if he did, he'd probably be unbeatable.
Gran Torino from My Hero Academia is an elderly pro hero who was friends with All Might and All Might’s mentor years ago. He’s likely in his 80s, but can still use his quirk “Jet” to move incredibly fast and overpower many opponents.
The Third Hokage, who despite being a decrepit-looking 70-year-old man, is extremely powerful and skilled, able to go toe-to-toe with the likes of the Big Bad Orochimaru. Many have called him one of the most powerful Shinobi to come out of the Leaf Village, perhaps equaling or even surpassing the late Fourth Hokage. A shame he dies, but even then he fights to the bitter end, sealing Orochimaru's arms and thus rendering them dead and useless.
In that vein we also have Jiraiya, who is the strongest of all three Sannin, could kill three paths of Pain (up until then, that was practically impossible), permanently kill one path, and was the master to Naruto himself. Not only that, his master, Fukasaku, an 800 year old toad and one of the most powerful beings in Naruto, is also this. How much does Jiraiya fit this trope? Every pupil who willingly chose to follow his example is a legend, spoken of with godlike reverence by others.
Subverted: the Old Master — who comes complete with mysteriousness, tea drinking, and repeated comments about today's youth — looks like a ten year old girl, has a crush on the main character's father, insists she is utterly evil, and makes at least token attempts to turn her students to The Dark Side whenever the topic of conversation veers anywhere near a decent opening. Well, that and an occasional detour into vamp territory, which generally fails spectacularly due to the fact that her main pupil/object of her affectionsis ten. Oh, and it is not just magic, for she has been studying Aikijujutsu for the past century and probably learned it from the fellow who originated same.
The Mundus Magicus arc introduced a straighter variant in the form of the former Ala Rubra member Jack Rackan, who acts as a somewhat goofy Obi-Wan towards the Ala Alba. Of course, the goofiness is a façade.
One Piece: Whitebeard, Sengoku, Rayleigh, Garp and Zeff among many others. It helps that if you're a pirate or a marine the only way you can live to see old age is by being stronger and more badass than everyone else. Minor character Lao G is a straight example though, being a 70-year-old who fights solely with martial arts and teaches hand-to-hand combat to the junior crewmembers of the Doflamingo Pirates.
"Silverfang" Bang from One-Punch Man is a martial arts instructor and the third highest-ranked hero in the world, although (like everyone else in the series) he's no match for The Protagonist.
Bang's brother Bomb also serves this role, being the creator of his own martial arts style. There's also Nichirin from the Council of Swordmasters, who trained Spring Mustachio and Atomic Samurai.
Happōsai and Cologne from Ranma ½ who are both 100+ years old and roughly one foot tall. While Cologne plays this trope straight, Happōsai more or less inverts it. He barely has any interest in martial arts, and his efforts as a sensei means he can, charitably, be described as a Fair-Weather Mentor. He's a major-league Panty Thief and Lovable Sex Maniac (only without the lovable), to the extent that he literally gets weak and sickly, losing the majority of his martial arts prowess, if prevented from stealing underwear and groping women. Yet, despite this almost completely opposed personality and the fact he considers being a pervert far more important and meaningful to being a martial artist, he is still an incredibly powerful fighter, capable of smacking down PantyhoseTaro with one of his normally firecracker-grade bomb attacks.
Saiyuki: When Genjo Sanzo meets Master Abbot Jikaku in the Burial arc, he seems like just a harmless old man- until he kills several youkai attacking a temple. Turns out he was once known as 'The Ogre' for his vicious training of would-be Sanzo candidates, including Sanzo's own master Koumyou.
In School Rumble, Mikoto finds Hinai training in the mountains, with an old man dispensing mystical-sounding advice. Mikoto Hinai if he's his sensei, but Hinai responds that it's just some random old guy.
Shaman King: When the zombie of Pyron, a martial arts actor, is released from control of Ren's sister Jun, Yoh's friends decided to call upon the spirit of Pyron's old master, Shamon, who was 96 when he died, to try and becalm the raging spirit of Pyron. When Shamon possessed Yoh, he quickly assumed a stooped stance, and didn't do anything... until Pyron tried to hit him.
Tears to Tiara's Master Ogam. While he spends much of the early episodes as the calm and serious old guy, it's not long before he breaks out his MAGICAL POWERS and blows up an ogre.
Tenchi Muyo!: Katsuhito Masaki in the OAV series (actually he's quite formidable in all of his incarnations, but...). Granted, he's really a young man — relatively; where he's from, 725 years plus or minus is considered youthful — masquerading as an old man, but even the trope's description warns us that looks can be deceiving. Capable of taking on even the most powerful villains in the galaxy and fighting them to a draw, if not actually winning...and this was at least in part because Katsushito felt his grandson Tenchi needed to defeat the villains himself as part of his training.
Toriko: Knocking Master Jirou fits the bill, as demonstrated when he effortlessly paralyzed a beast that took the combined might of Toriko and Coco to bring down. Later on, the IGO president shows us that he also qualifies.
Four for Miyamoto Musashi: his father Shinmen Munisai, Houzouin In'ei, Yagyuu Sekishuusai are all Musashi's Old Masters (to a point), yet subvert the trope in their own ways: Munisai wasn't much of a master (his obsession with being "invincible under the sun" actually left him closing off his world, fearing his own child and pushing away others), In'ei was actually Inshun's Old Master and trained Musashi because no one else could threaten Inshun's life and thus get Inshun to develop further, and Sekishuusai is 'just' an old man who's since retired, passing down the system to his son; what he does impart onto Musashi is one of the most profound lessons, after Musashi defeats himself by internalizing the idea of "the invincible Sekishuusai" until it becomes a Self-Fulfilling Prophecy: "Invincible's just a word."
Sasaki Kojirou's adoptive father Kanemaki Jisai subverts the trope too: living by the sword has left him unmarried, without children or friends, and thus hopeless... until Kojirou comes along; at that point, he advertises himself (unsuccessfully) as an Old Master to make a living so that he could raise Kojirou away from the sword. When Kojirou shows a terrifying affinity for the sword (by disarming an evil Old Master and then attacking the corpse) however, Jisai spending the next half of the boy's life embodying the phrase "old age and trickery beat youth and speed," trying to repeatedly dissuade the boy by defeating his challenges with cunning and underhanded means... until his former disciple Itou Ittousai comes along and secretly takes Kojirou under his wing. After he finds out, Jisai reluctantly gives up Kojirou into Ittousai's custody, thinking that he gave his life to the sword only to have nothing but regrets... until he finds that although he couldn't keep Kojirou away from the sword, he did raise a decent man with great potential. "My life dedicated to the sword — it was worth it all. It was worth it because I managed to leave behind a great swordsman like you..."
