No. Chaos (as Chaos 0) is seen after the battle with Tikal.
In Sonic Adventure, Perfect Chaos is the Chaos Creature when it has its tail and the 7 chaos emeralds.
In Sonic X episode (around) 32 Sonic defeats perfect Chaos as Super Sonic, and Chaos and Tikal disappear into the sky, after that Chaos is not seen again in the TV show.
According to Sonic the Comic when Perfect Chaos attacks Sonic he absorbs the Chaos energy!
at the end you turn super sonic and kill chaos.
he is in station sqare when you are gonna fight him
This is really easy actually just run toward the speed boosts to make super sonic go really fast which when you go into perfect chaos he will reach his brain and attack it which will damage him i believe you have to do that 3 or 4 times though he will revive and it will get harder to do this. MAKE SURE YOU GRAB RINGS!
Can only play as Super Sonic in the final boss against Perfect Chaos.
Chaos is a Water-ish type of creature who came from the Master Emerald, also if you feed him a Chaos Emerald, he will turn more powerful: Chaos 0, Chaos 2, Chaos 4,Chaos 6 & Perfect Chaos.
Not in Sonic's Story, but if you finish all of the storys, you get a new story to finish called 'Supersonic Story" where you fight Perfect Chaos, the strongest form of the evil creature in Sonic Adventure DX called Chaos.
i think your talking about Perfect Chaos he's not a hedgehog, he is the gardian of the little creatures called chaos (pronounced chows)
Sonic Chaos happened in 1993.
Mephiles did kill Sonic but Sonic was later resurrected with the power of the Chaos Emeralds and a kiss from Elise. He killed sonic by coming out of the ground and and blasting him with the power of the purple choas emerald (sneak attack).