Complex sentence: When Unicron tries to destroy Cybertron, his energy was sucked out of him by the Autobots which restores Megatron to life Afterwards, he disbands the Decepticons realizing the error of his ways and retreats to parts unknown.
Split into simpler sentences: When Unicron tries to destroy Cybertron, his energy was sucked out of him by the Autobots which restores Megatron to life. He then disbands the Decepticons, realizing the error of his ways, and retreats to parts unknown.