I have a personal headcanon that Aeon Hero (SKC Galacta) is what Galacta Knight was like in his prime before being sealed.

If you compare the two, Aeon Hero has bigger wings and more power than Galacta. The cramped crystal probably caused his wings to get smaller and his power to weaken. Which is why with each Kirby game his battle gets harder and more intense due to being free from the crystal. So we're not defeating Galacta Knight, we're slowly reawakening his powers. Thanks for reading, have a great day!