In one memorable occasion Mitsuhashi beat up the entire male student body of another school by himself to recover Kyouko's stolen bag. How? When he noticed he was up against the entire school he ran until they were all lined up and forced to stay lined, and hen punched the first. A domino effect later, every male student had a broken nose and no willingness to fight anymore.
Mitsuhashi, Itou, Imai, Koyama and Nakano (and Tanigawa, but even Imai forgot about him) storming Akehisa High, stealing back the money they had extorted from the students of Nan High and beat the new head up. And getting away with it. The stormers became heroes, while Akehisa's reputation took such a beating that the following day all the students of other schools bullied by Akehisa showed up to finish the job: they didn't fear Akehisa anymore.
Akehisa's answer to the second storming? They countercharged and chased them off. It took Katagiri (who hadn't graduate yet due a long detention) face the stormers on his own for the rest of the school to countercharge, but they did, and they won.
Speaking of Tanigawa and Akehisa High... In the manga version of the Akehisa's debut arc, Tanigawa manhandled an Akehisa punk twice his size! The punk had grabbed him by the tie, and Tanigawa just pinched his ear and was making him submit. Granted, Tanigawa ended having his ass kicked, but that was only because Sagara showed up...
From the same arc, Satoshi Katagiri had one when fighting Imai... And defeating him with one punch. True, Imai is often used for The Worf Effect, and was weakened by one of Sagara's beatings, but even in those conditions he can usually tank a few hits... Yet Katagiri needed just one punch.
This was immediately followed by Katagiri fighting Mitsuhashi, with them being evenly matched. Katagiri was stronger, Mitsuhashi was faster and sneakier, and none could prevail before the police showed up.
In their final battle in the arc they finally managed to fight without being interrupted for a while. We don't see what happened, but by the time the police interrupts again Mitsuhashi has almost won, and Katagiri is still standing only because of his pride as the head of Akehisa. Mitsuhashi's awesomeness for this victory is increased when Katagiri gets some heat by the previous head for his near defeat and reacts by knocking him out with one punch.
It was actually a man in a suit trying to scare Mitsuhashi and co. away, but Mitsuhashi never found out... And it takes a lot of courage fighting what you believe is a bear unarmed.
How does Itou fight a kendo champion? He grabs a giant pole and swings it at the champion. He failed to actually lift it enough to swing it, but the sight of him lifting him that much caused the kendoka to faint in terror.
The final battle between Koyama and Imai. Koyama, a gigantic transfer student to Beni High after being expelled from Chuu High, tried to beat up Imai and take over the school because he did not respect anyone weaker than him, but in their final battle Imai, weakened by Sagara having broken his pinky in the previous arc and realizing that his enormous foe was just too big for his Signature Move of grabbing his foe's face and throwing him away, grabbed Koyama by the stomach, lifted him over his head and threw him in the trash. Koyama was so impressed that became Imai's loyal follower at once.
Imai versus the Gokudo Syndicate. He was so formidable he could take down the first of their men while sitting on a bench, and they were no match for him. The last survivor only took him down by pretending they had taken Riko hostage...
Yanagi's defeat in the Hokunei arc. Yanagi was a Knife Nut, so what did Mitsuhashi bring against him? A ping pong racket. That he used to block and catch all his knives. That triggered an hell of a Villainous Breakdown...
Earlier in the fight, Yanagi tried to throw a knife at Itou... Who charged on faster than Yanagi could throw his knife. And was disarmed. For obvious reason, Yanagi's Villainous Breakdown got worse as soon as Itou caught up to him...
And when Imai and Nakano caught up to him too, Yanagi's Villainous Breakdown reached the point he ran to the police and begged them to arrest him.
Earlier in the arc, Itou lost to Ootake, Yanagi's right hand man, due believing that Ootake was only trying to defend another's school student (it was part of a plan to make him a willing Scape Goat in case Yanagi or him committed a crime) in a mistake, and thus being unable to muster the will to fight. After discovering their plan, Itou fought Ootake again... And dropped him with three punches. Keep in mind that Ootake was taller and larger than Imai...
Upon transfer to Nan High, Takasaki decided to track Mitsuhashi down and give him a lesson for cheating at a marathon. As he searched for him, half of the punks of the school tried to beat him up... And were sent flying without landing a single hit.
In one arc a group of Tokyo delinquents went in Chiba to mess with Itou and Mitsuhashi. They got served, but their boss Shirohara managed to escape unarmed, and was safe in the knowledge they wouldn't be able to track him down, not knowing his true name and him leaving delinquent life... Mitsuhashi cocked up a story in which a person with his face had saved his non-existent little brother, getting Shirohara some fans who contacted Mitsuhashi so he could come and thank him in person. Shirohara's Oh Crap face was comparable with the epic Eneru from One Piece.
What did Mitsuhashi and Itou did him? In order: they beat him up; made him pay for a wall he had wrecked in the process; forced him to host them in his own home; got him to show a bit of his true colours; and duped him into admitting a beating and a theft (that he believed Itou and Mitsuhashi were framing him for) in public. Then they mocked him for being completely alone now, and left.
Mitsuhashi versus a member of the Karate gang. In a friendly spar, Mitsuhashi had lost to him. In a brawl where Mitsuhashi got serious... It was a Curb-Stomp Battle in Mitsuhashi's favour.
In the spar, Mitsuhashi had lost when he had dodged a kick by jumping only to be kicked in the leg in mid-air. In the brawl, Mitsuhashi dodged the same way... And dodged the same kick by rotating mid-air and kicking his foe in the face.
Also, Itou versus one of his pals. He kicked Itou's leg to stop him... And Itou, in spite of the pain, headbutted him into unconsciousness.
In the same arc, Kurosaki's return. In his debut, he was no match for Mitsuhashi. Here, after taking a few levels in badass, proved capable of taking down the members of the Karate Gang in one-on-one combat faster than Mitsuhashi did. And he was injured to one hand due them having previously attacked him all together.
At the start of the Saipan arc, Imai knocked out Mitsuhashi and Itou with one punch each, over the tickets for Saipan (that Mitsuhashi had won with lottery tickets stolen from Imai). Of course Mitsuhashi and Itou inflicted him a No-Holds-Barred Beatdown as soon as they recovered, but still...
Then Tanigawa decides to give Jun a lesson... And tricks him in revealing his true colours before a girl he was chatting up into lying with him. And then beats the crap out of him, at least until Jun gets help by one of his friends and whips out a revolver.
Topped by Tanigawa. After getting the drugs Jun planned to have his bud smuggle in Japan, he wonders what to do with them, says he'll give them back to Jun... And then tosses them in the ocean and dares Jun to do something about it. He killed Jun's will to fight, with that.
Chapter 343, "Midnight Run!", is obviously very fun due the consequences of any attempt at stealing from Mitsuhashi (that and the loot being a wallet containing 417 yen and a phone card), but in the attempt to escape from Mitsuhashi the Smoking Thief showed us Roof Hopping, even between two condominiums with a large gap, and Mitsuhashi not only matched everything but the last (he threw a bucket at him to finally catch him), but did it immediately after waking up and barefoot. And, for a brief moment, outran a bike.