Complex sentence: Dr. Guardian helps Daisaku and Jūrō escape, only to be shot to death, but not before he set an atomic bomb that destroyed the base, the resulting explosion activates the giant robot, which moves to Daisaku's every command.
Split into simpler sentences: Dr. Guardian helps Daisaku and Jūrō escape, only to be shot to death, but not before he sets an atomic bomb that destroys the base. The resulting explosion activates the giant robot, which moves to Daisaku's every command.