GP 7: Being chomped down alive by the misunderstood Carrigator, Gunpherd told Gunpei to run away. Gunpei refused; they're partners and if they die, they'll die together. This camaraderie impressed Carrigator, who previously didn't think high of humans, and he joined the team, giving access to GunBirOh.
GP 9: Saki and Hant faced off against a large horde of Uguts in an abandoned factory, starting with a chaing-swing entrance a la Tarzan and using whatever they can to their advantage. They're in a totally different dimension which supresses their power to transform, mind you.
The debut of EngineOh G6 in GP 10. Renn deserves the credit too, since it happened from his idea and effort.
The whole GP 11 for Gunpei: With the whole town, including his friends, under hypnotic suggestions of Antenna Banki through TVs, he himself wanted by the police, and the whole team on the verge of being disbanded, he stood up to the Monster of the Week alone while shouting that his friends won't be held back by lies and facades. His True Companions speech did snap them out of the spell completely, and they came to his rescue at the last moment.
The Engines overcoming their fear of Hiramechimedes in GP 15, after which everyone worked together according to Saki's plan to take him down. It succeeded. Although it proved to be insufficient to defeat him, this is the first time they were able to match him ever since he first appeared.
Gunpei has yet another in GP 19, when he realized that he's neither a "pro" nor an "amateur"; he should just leave it to his instincts like he always did. He actually pulled through, and this impressed the Wings, whom he was trying to unsuccessfully convince early in the episode that they're not wimps.
The Chainsaw Banki episode and Jum-bowhale's debut. The battle between Chainsaw Banki and the Wings' leads up to an old warehouse being filled with floating sawdust, and then it all gets ignited... possibly a CMoA for Super Sentai in general, as the first humongous explosion to be completely justified in-universe.
The team's victory over Detaramedes* Hiramechimedes gone insane from Bikkurium self-overload. in GP 23 can definitely qualify. Sōsuke in particular deserves the biggest credit, because it's his Hot-BloodedIdiot Hero antics that saved EngineOh G9, and defeated Detaramedes.
What, no love for the 6 vs 1 unmorphed fight between the remaining Go-Ongers and Yogostein?
GP 37 begins with the Dino Engines in a Heroic B.S.O.D. while the others face a new Engine Banki, who curbstomps thre mecha at once, but blasting Engine-O apart leads to Speedor taking him on aline, and blasting him back leads to SŌSUKE leaping headlong into it. Bear in mind that the following year's Shinkenger employed this similar tactic, but ended it one step early.
In GP 38 Saki and Miu basically had a Dethroning Moment of Suck when they got their butts kicked by Shower Banki and behaved like frightened rookies, revealing the guys were frozen in the process. But they wouldn't take that sitting down, they along with Bear V in Go-Roader took out Shower Banki and their DMOS showing total girl power and awesomeness. All with the G3 Princess rap in the background.
In GP 49, Kitanedas and Kegalesia finally decide that they had enough of Yogoshimacritein and destroy the Infinite Wastebin, telling him that Gaiark is supposed to give their kind a home, not turn Yogoshimacritein into a supreme dictator. They are then killed, but it definitely shows that the original ministers, while ineffective, were not to be messed with.