Don't worry, its actually common for enemies in the beginning to be hard and take effort to destroy, but when they get revived, they get killed off ridiculously easy. Just look at how in Megaman NT Warrior Axess, the Darkloids took so many episodes to destroy, but then when they all get revived, they get killed in one shot, each and every one of them.



Or again in Stream, with the even stronger Asteroid Navis, who are so strong before, but then when an army comes of them, they get one shot killed.