Final Fantasy I
Voice Actor: N/A
Chaos is the final boss in the original Final Fantasy game, but he only appears towards the end of the story. This is because he is actually Garland, or more correctly, Garland after he absorbs the power of the crystals and transforms.
When the Warrior of Light travels two thousand years into the past, he confronts Garland. To try and preserve his pact and allow him to live forever, Garland absorbs the powers of Lich, Marilith, Kraken and Tiamat and Chaos is the result.
This isn't enough though, and the Warrior of Light successfully defeats Chaos. This causes Chaos to disintegrate and cease to exist.