In Der Monster Klub, not only does Randy battle against 4 stanked kids simultaneously (and win), he used their attacks to get closer to the object he needed to destank!
Stank Like Teen Spirit: Howard quickly realizing what the cause of the stanking was with Randy and formulating a plan to cure it. Howard's mad chess skills manage to beat Viceroy's specialized robot and curing nearly everyone in the student body. Then Randy disposes of the robot quickly with his Ninja Hot Balls.
Randy Air-Fist punching the Sorcerer in "Raiders of the Last Nomicon"
Not to mention escaping Mc-Fist's lair using knowledge he gained in previous episodes.
Randy and Howard fighting the fused stank form of flute girl and Stevens and getting the Sorcerer's key.
Less awesome, but still so, is Flute-Girl(And several others) dumping Stevens.
Randy chasing after the Magically empowered McFist doom robot, without his ninja suit because it has Howard. When it jumps off the dam, Randy dives after it.
Mac Antfee and Randy battling inside the Ninjanomicon without the suit. In spite of having less experience, Randy beats him by tricking Mac Antfee in to opening the Ultimate Lesson Door.
Howard throwing that cinderblock and temporarily knocking out Catfish.
In a clever move, Viceroy exploits Howard's destructive abilities to find the flaws in his so-called 'indestructible' objects and used them to create an unstoppable robot. Then Howard one-ups him by still helping Randy beat it by luring it to the site where a satellite crashing was bound to happen.
Randy accidental ricochet shot with with Theresa twirling sticks was pretty impressive.
When Randy prepares to sacrifice himself by forcing himself and the Sorceress into the Realm of Shadows, Howard immediately goes and rescues Randy before he becomes trapped as well.
"Randy Cunningham: 13th Century Ninja" Has ton of these.
The Sorcerer showing just how much havoc he can raise when freed, both in the past and the present.
Randy holding his own against the Sorcerer before breaking the Tengu Stone and having it possess Howard. Because the Tengu and Ninja suit are linked, Randy combines his fighting experience with Tengu Howard's might a-la video game style, with the Sorcerer summoning an aura clone to help him.
Then there was the First Ninja himself coming back and saving Randy and Tengu Howard before they along with the Ninja's squire seal away the Sorcerer and undoing the damage.
Speaking of the First Ninja, he has some sort of Mystic DRAGON PUNCH, which Randy asks him how to do it.
Principal Slimovitz and what's left of the Norrisville High student body organizing a resistance movement against the Sorcerer.