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.
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.