In the first story, after Grimm handed Kim a Curbstomp Battle, how did Kim take the lead in the next fight? She gives Grimm a taste of his own medicine, playing with his insecurities about romance which she knew all too well. Grimm, despite going in knowing it was likely a trap, falls for it hook, line, and sinker.
"The Return of Zorpox" has Kim show that she was not sitting on her laurels between stories and had learned from her defeat at Grimm's hands, and had tightened her combat appropriately, getting a hard hit on Grimm and then blowing him through a closed manhole. Subverted, however, in that Grimm simply allowed her to get the win so Ron could use the Lotus Blade to slap a feedback modulator onto the battle suit.
The Cavalry both times in "The Return of Zorpox". First the Yamanouchi students out right No Sell the Mega Synaptic Transducer thanks to their mental training (whereas everyone else is falling to it's power). Then, Kim's most well known enemies show up and help her fight Ron. The second one is perhaps the one time that Zorpox the Conqueror has lost his cool and has no contingency plan ready. Instead, he resorts to throwing everything he has at them in frustration.
Although she lost, Kim still managed to last against Ron's MMP for a long time, with it being required that Grimm, Rhonda, and the Mega Bots dogpile her after she had worn herself out fighting him. The second time they go one-to-one, Kim manages to outwit Ron's use of the Lotus Blade to expose him to a powerful kick that knocks the weapon right out of his hands.
"Back to Kwitcherbeliakin" has Rhonda step up - empowered by the Great Bear, she utterly demolishes Maze's shadow defenses, beats him senseless, and then when Maze sends Grimm flying off a cliff she leaps out, grabs him, and manages to save all their lives while leaving a large crater where they landed due to her power usage. Even Maze is stunned by the sudden display of power, having previously dismissed her as a bumbler.
Adrenna Lynn is back, and she has Taken A Level In Badass... as a thief who dodges and evades rather than try to overpower Kim like Shego does, giving herself a distinct identity as a villainess.
The first few chapters of "A Friend in Darkness" pits Rhonda against several different people. While each use is a great showing of Rhonda's newfound powers, each of her opponents manage to fight back.
Hego manages to match her strength for strength, up until Rhonda hits him with her Spirit Strikes and shuts down Hego's powers with them.
Although the story and characters treats it as if Rhonda had decisively defeated Kim, when reading the actual battle it's quite clear that the two are stuck in stalemate. Rhonda simply can't make enough meaningful hits on Kim - even her homing Spirit Strikes are dodged - and the only reason Rhonda doesn't walk away much worse for wear is because MBP seems to have given her fab abs. And unlike the other two in this list, Kim is not defeated at the end of the fight, simply kept at bay long enough for Rhonda to flee with the job done.
Ron, after embracing his MMP, goes to town with her and they fight on equal terms until Rhonda uses her spirit strike to disable MMP and then Monkey Fist and Maze show up and banish both of them.
"A Friend in Darkness" has both teams helping the other in one of their normal missions. Grimm manages to trick Gill into thinking he's Ron, then pouring enough salt on him to cause serious damage. Kim manages to evade traps that caught both Grimm and his friend Enrique, saving all of them from Mister Matter's rogue henchmen who were throwing the whole arsenal at them.
Ron using his MMP to send Maze flying in "A Friend In Darkness". Heck, both the climatic battles in that story qualify.
Tara standing up to Bonnie for Kim after she temporarily breaks up with Ron. Shows that she's not just a Brainless Beauty.
Similarly, Rhonda walks out on Grimm when he wants to make Kim and Ron's breakup permeant. She's no longer just repeating his philosophy at good guys as she was in "The Return of Zorpox".
In "Graduation", Rhonda takes up the mantle of Proxorza the Liberatrix in order to do heroics behind Grimm's back. She manages to, in a short time, rope Jade into helping her and making her a battle suit variant, terrifies Mister Matter without even hindering his operations, and manages to go toe to toe with Grimm, both in head gaming and hand-to-hand combat. Note that the last feat she had to do without MBP as Grimm would recognize that in a heartbeat.
Credit must go to Jade in the second one, as she managed to juggle both Grimm and Rhonda's mission control without Grimm becoming aware that he was being played.