During the first season's two-part finale, Grendizer has been beaten by a pair of giant robots, Duke Fleed's nemesis Blacki has taken control of the Science and Space center and is torture Dr. Umon, Koji's TFO has been damaged too much to help, and the titular mech is forced into hiding. When he makes his comeback, Grendizer not only engages in a duel with one of the enemy mechs (who uses similar melee weapons as Grendizer) in a crumbling cave, he leaps up, shoots lasers so he can bore his way back to the surface, decapitates the five-headed mech, and then flies straight at Blacki's command ship in a game of chicken. And he wins. Until Mazinkaiser came out, this was the most badass thing done in the Mazinger universe.
Daisuke was struggling through a battle, and Kouji needed aiding him with the Double Spacer, a flying ship could be attached to Grendizer to increase its fighting capabilities. However, Kouji was bedridden and he could not pilot it. So Hikaru, fed up with being a helpless victim, enters the cockpit, rides the Double Spacer despite of having no previous training, manages successfully combining with Duke after several missed tries, and together they defeat the Monster of the Week. She exhaling out a sigh of relief as Duke's voice sounded through the communicator calling Kouji (since he thought his friend was piloting it) made the moment was very heartwarming, too.
In one story of the Nagai's manga, the Vegans brainwashedKouji and Tetsuya into attacking Duke at once. Grendizer fought Mazinger Z and Great Mazinger at once -that is a Crowning Moment of Awesome in itself-, to a stalemate, and he managed slicing off one of the arms of Great Mazinger.