In the cartoon, the Decepticons were led originally by Megatron. During the attack on Autobot City, Megatron and Optimus Prime fought, and both were heavily wounded. Megatron was turned into Galvatron by Unicron. Galvatron become senile, and wasn't always that great of a leader. The Decepticons were hurled out into space by Fortress Maximus when they were all in Scorponok, and haven't been heard from since. However, their decendents are the Predacons in Beast Wars.