The only genuine such moment - and probably the only proper crowning moment Admiral Daala ever manages - occurs in Darksaber when she gasses the Imperial warlords and unifies all of their fiefdoms when it becomes clear that they won't stop their feuding and fight the New Republic. Too bad her absolute failure to capitalize on the result undermines it.
During the attack on the Jedi Temple in Darksaber, R2-D2 destroys an AT-ST walker by himself by luring it into a hanger and crushing it beneath the blast door. He even whistles a victory cry and resets to do it again.
The biggest has to go to Dorsk 81. Unsure of himself since he left home, he finally gains full confidence in his abilities. He calms down the Jedi trainees and has them pool their strength. Using that strength, he use the Force to physically push 17 Imperial-class Star Destroyers completely out of the star system. It kills him, seemingly cooking him from the inside.