Complex sentence: The tyrant Megazarak begins the Decepticon movement and thus, the Great War, becoming a violent dictator and imprisons most of the city-state Kaon, making it the Decepticon capital.
Split into simpler sentences: The tyrant Megazarak begins the Decepticon movement and ultimately, the Great War, becoming a violent dictator. He imprisons most of the city-state Kaon, making it the Decepticon capital.