Professor Yumi has several moments throughout the series. In episode 17, Dr. Hell created a Robeast (Holzon V3) could cause earthquakes. After displaying his power on a Japanese city like an object lesson, Baron Ashura threatened with obliterating Tokyo unless Dr. Hell was named director of the Photon Institute (with full access to the Photon technology and the Japanium lode, of course). Japanese people rioted, demanding the Government agreed and the Government so did. Later Baron Ashura showed up on the Institute's main door with several dozens of armed, mechanical-horse-riding Iron Masks surrounding the place and the implicite promise of making Earth swalloed all of them if the did not happen. What Did Yumi did? He told: "No.". And then he implemented the plan to find Holzon V3 and destroying it, what Mazinger Z did by ripping its legs off its upper body when it tried burrowing to safety in the ground.
Episode 28: Ashura is holding Professor Yumi hostage atop from a cliff to prevent Mazinger and Aphrodite from fighting back Hogus D5. Yumi begs them fighting but they do not move. Then he thinks if he dies they will fight to avenging him, so he wrenchs away the Iron Mask holding him and dashes off the cliff! However Kouji saves him by quickly shooting Mazinger's fist to catch him.
Episode 29: Kouji fought against Grengus C3, a gladiator-alike Kikaiju with two iron balls attached the arms by chains and a crest jutting out of his head in reality was a flying, heat-emitting disc. Grengus started the battle by hitting the surface of the lake where they were fighting to splash the Pilder's cockpit and blind Kouji, and then it began whipping Mazinger-Z, breaking down all its weapons with a few hits. Then it trapped Mazinger's arms with its whip-like chains, shot his flying disc to embed it into Mazinger's chest, setting the mecha afire, hauled Mazinger and made it spinning for a while before dumping it in the lake. Then Grengus went on its way like if nothing would have happened. Later Kouji returned for a rematch -naturally-, and he was being stomped again. Then he won by turning Mazinger's engine OFF and then turning it on again on the exact moment to catch Grengus unbalanced, hauling it with its own chains and slamming it on the ground.
Professor Yumi got another awe-inspiring moment in that episode. When Grengus was flattening the Institute, Yumi ordered everybody go out of the building... but he refused leaving.
Episode 32: Kouji, unable to fly at that point in the series, pursues a flying monster by grabbing Aphrodite A's breast missiles and using them to fly. Now that's manly.
Episode 34: After a long-running subplot where Dr. Hell had been sending flying mechanical monster after Mazinger Z, Professor Yumi and his colleagues have managed building the Jet Scrander, a device will let Mazinger fly. Enraged, Baron Ashura sends a new flying Kikaiju, Genocyder F9 to lure Mazinger Z out of the Photon Institute, as an iron mask infiltrated into the Institute tries blowing up the device. Fortunately he is stopped, but Genocyder F9 is trashing the Institute, and Kouji has to rush back to the place and performing a hasty docking maneouver with the Jet Scrander, something he has never tried before. Fortunately, Kouji performs succesfully the maneouver and Mazinger flies for first time, defeating Genocyber F9 in a spectacular aerial battle.
Episode 36: Kouji is fighting Granada E3, a Kikaiju loaded with missiles nuclears. To prevent it from dump them on the nearest city, Kouji flies upwards, using HIMSELF like a bait for a monster armed with nuclear weaponry. Then Granada shot one of its missiles at him, and Kouji hit it with a Breast Fire. The ensuing nuclear blast struck both giant robots, and Granada E3 was blown to smithereens, but Mazinger-Z withstood the nuclear explosion, keeping Kouji alive. This episode proved you need more than a nuke to destroy Mazinger-Z. How Badass is that?
In episode 48 Boss Borot shows up. You can see from the beginning it will be a Comedic Relief character. Then Boss and Aphrodite manage to rip the limbs off of the Monster of the Week to let Kouji beat it.
In episode 49, after countless humiliations delivered by Mechanical Beasts AND Kouji, Sayaka AT LAST manages to defeat a Mechanical Beast (Gumbina M5) using a Go for the Eye tactic. The moment is done more awesome by the fact of that was one of the best Robeasts built by Hell, and it was completely trashing Mazinger.
In episode 53 Mazinger-Z is nearly completely depleted from energy during a battle, the control deck is smoking and giving off sparks due to the strain, the weapons don't work, Prof. Yumi is ordering -''repeatedly- Kouji retreating because he'll die otherwise... and Kouji simply folds his arms across his chest as he calmly waits for one chance to blast the Beast down! It is hard to convey how Badass he seemed right then.
In the manga episodes penned by Gosaku Ota, during the final battle Dr. Hell orders Count Brocken go and battle Mazinger... in spite of Brocken was a normal-sized human and he had no weapons to take down a Humongous Mecha! Brocken reluctantly agrees... but before leaving he tells EXACTLY what he thinks of Hell, calling him out on all his failures and flaws, blaming him for their defeats, bitterly stating he does not care his troops risk their lives everyday, and making very clear he served Hell out of gratitude -for saving his life- but he never wanted working for such an inept. Then he announces if he survives he will return to Germany before leaving to fight as Hell threw a fit.
Everything what Tetsuya does. EVERYTHING. If he shows up, you know it will be awesome.
The entire final act of Mazinkaiser: Shitou!! Ankoku Daishogun is one big Crowning Moment of Awesome as Kouji Kabuto Pilder Ons Mazinkaiser as it's descending from space, crashlands, then goes off tearing the Mikene Empire apart. When Ankoku Daishogun crashes his ship into Mazinkaiser, it tosses it off, then slices it in half with the Kaiser Scrander. And when Daishogun has them on the ropes, Kouji's egged on by the spirits of those who died and he has his And This Is for... moment before decapitating Daishogun with a point-blank Turbo Smasher Punch and gutting his body with his own sword!
Mazinkaiser is dropped from space, re-enters the atmosphere and crashlands so hard that the surrounding enemy robots are melted by the resulting explosion. Then it climbs out of the crater without a single scratch, due to being Nigh Invulnerable.
Despite being the Butt Monkey of many jokes and pranks, Boss and the Boss Borot ends up getting plenty of Crowning Moments, especially in the later series. In Mazinkaiser, he battles Dr. Hell's Machine Monsters by himself, giving time for Kouji to get into Mazinkaiser before being destroyed. In Shitou!! Ankouku Daishogun, he beats a Mikine General with a chain and reveals he hid Kaiser Pilder inside the Borot for safe keeping! And in Shin Mazinger, when Kouji prepares for the 100 Rapid Rocket Punch, he hovers the head of Boss Borot over the wreckage that Mazinger-Z's stuck in and pulls it out with a giant magnet so Kouji can finish the fight!
Boss's defining awesome moment, though, is him taking on Machinebeast Serpenter I6 on his own with no weapons at all and a previously damaged Borot - and winning. When asked how he did it, he pointed out he promised Kouji he'd keep the Machinebeast off his back, and if there's one thing Boss doesn't do, no matter what, it's break a promise.
Anything Koji does when he is fighting OUTSIDE of the mecha. Two things of note, are the Robot Mutilation backdrop that he does against Gamia Q, and Shooting with Photon powered gun and using the beam to cut in two.... Gamia Q
In Shin Mazinger episode 3, Baron Ashura is so pissed by the appearance of Mazinger Z that he runs across water, jumps hundreds of feet through the air and then dropkicks it in the face. This is followed by a Master Asia style beatdown of Z and Aphrodai A with just his/her BARE HANDS.
Also in Shin Mazinger, Juzo snaps Kouji out of a Heroic BSOD by surfing a Rocket Punch through the air and using it to punch a hole through the enemy robot that had Kouji pinned down, just so he could access Z's cockpit.
Viscount Pygman finds out that he can't direct any attacks against Tsubasa, because of some kind of biological programming she did to him. So how does he get around it? He stabs his eyes out so that he won't be able to recognise her, enabling him to attack.
Pretty much all of episode 10 following Cross'Robotic Reveal. The true nature of the Kurogane House members is revealed and they deliver a huge beatdown to the Gamia sisters with their crazy weapons and super abilities.
Near the end of episode 13, when Mazinger Z is incapacitated and the Pilder is grounded, Kouji and Ankokuji are attacked by a Mechanical Beast. Cross shows up to lift up the Pilder and give Kouji the opportunity to fire its missiles and destroy the thing. That's right. They beat a Monster of the Week without using the titular mech.
Zeus. Rocket. Punch. With his own severed arm no less.
You forgot that beforehand, Kouji dual rocket punches Hades, the literal God of Hell, in the face eyes while standing on Zeus' shoulder.
The mere existence of the Big Bang Punch is awesome in itself, being that the robot actually transforms into a giant Rocket Punch. Of course the true CMOA is its first use, where rips the powered-up Energer Z apart and then punches it into space.
The end of episode 23 was overflowing with awesome manitude. Earlier in the episode, Kouji gets an invitation to duel with Baron Ashura, with the winner gaining the Photon Power Labs. Kouji initially declines. But then he has a change of heart. Because ultimately, he is a man, and men don't turn away from challenges, even if they know full well that they are about to walk into a trap. This is accompanied by Kanjite Knight blaring in the background, hot-blooded narration and Mazinger slowly marching towards Ashura in the sunrise, not even flinching when Ashura predictably reveals that he/she brought some 6 allied machines with them.
Professor Yumi's unveiling of the Fortress of SCIENCE! from the wreckage of the Photon Power Labs, followed by him switching gears from "meek-and-modest professor" to "Awesome Large Ham" as he orders a photon laser barrage on Bardos Island and its armies.
At the same time, the once thought dead Mazinger Army return in their pilders and show what "Mazinger Army" really means - the Fortress of Science is packing hundreds of copies of their machines, which all burst out at once and join in with the assault on Bardos.
Gamia's tug-of-war with the King of Hell, using her hair to pull it and the Fortress of Science.
In the final episode, its the ONE HUNDRED ROCKET PUNCH!!! THEN THE FISTS GET COLLECTED AND IT BECOMES A GIANT FIST BY ITSELF AND RIPS DR. HELL'S ROBOT APART! FOLLOWED BY KOUJI'S BIG BANG PUNCH!!!
Perhaps most memorably of all, in the last five minutes of the series Baron Ashura, after a whole series of being mocked and failing and being trodden on, succeeds in screwing over the entire cast with a brilliant plan. Even though it might spell doom for the protagonists, most fans consider it a truly awesome moment.
In Shin Mazinger Zero, Kouji takes the Rocket Punch to a whole new level by RIPPING HIS OWN ARM OFF and throwing it at the enemy, fist still clenched. It busts a hole right through them.
Shin Mazinger Zero, chapter 7, Sayaka destroys three mechanical beasts, and what makes it especially awesome is that 1) These same mechanical beasts had been giving Kouji major trouble 2) They're the ones from the anime, in particular, the ones from the ep where they were attacking Japan in three locations, and she ended up the Damsel in Distress. Also a Crowning Moment of Funny due to the reason as to why Sayaka is so pissed off and competent.