The ending of the final episode of Reideen, seen here SaveFrom.net. Pulling your final weapon out of the Moon surely qualifies as your crowning moment.
The second-to-last episode of Kotetsushin Jeeg, a sequel to the original Kotetsu Jeeg, has both the original Jeeg's pilot and the new series' pilot both become their respective Super Robots and beat the ever loving hell out of everything around them.

Seeing Hiroshi Shiba shout out "CYBORG CHANGE!" for the first time in aeons is... beautiful.
Much agreed - but this troper think the scene could only have been more epic (if that's possible) if they'd kept the original voice actor for Hiroshi. It doesn't lessen the scene, but damn it would have been awesome.
Even if you were too young for the original, you could tell this was the stuff of legends.
Speaking of Hiroshi himself, earlier in the same episode while he has to protect Big Shooter: "I can no longer become Jeeg. My fists are more than enough for you! Come at me, Haniwa Phantom Gods!", and when Kenji and Tsubaki return from their objective, you briefly see a pile of shattered clay phantoms in the foreground.
Not to mention the line he gives before the double Jeegs fight. "Hey, there's no air out there!" "I don't need it." Before jumping out of his spaceship and onto the moon.

A mention must also be given to Combat Mecha Xabungle and it's infamous ICBM catch SaveFrom.net.