The Shadow Dragons

The new dragon turns out to be pure evil. He sucks up the Dragon Balls and creates six new dragons, and the seven of them fly away. Elder Kai explains that each time the Dragon Balls are used, they store negative energy, and that energy takes 100 years to dissipate. The reason the balls scatter after they're used is to give them time to release their negative energy. But because Bulma invented the dragon radar, they were able to find them very quickly. This overuse caused the balls to overload themselves with negative energy, and that energy spawned the Shadow Dragon. Feeling guilty for his role in using the Dragon Balls so often, Goku takes up the challenge of defeating the dragons, because if they're not destroyed, they will annihilate the entire universe. Goku follows the destructive path left by the dragons, and Pan follows him, bringing Giru along to use the dragon radar. They find the two-star dragon destroying a village.