Things You'll Need
Instructions
Wait for the Chao Egg to hatch.
Raise the Chao any way you wish. Any actions at this point will only influence the stats of the ultimate Chaos Chao. Your actions will not influence your ability to actually breed it, though.
Wait for the Chao to die. A Rebirth Egg will be left behind when it does. The Chao will die after about 20 hours has elapsed in "Sonic Adventure 2: Battle." Some actions can slightly increase of decrease the Chao's lifespan. There is no reliable way to decrease the Chao's lifespan noticeably. Do not feed the Chao strong fruits if you want to minimize its lifespan, because these will noticeably increase the length of the Chao's life.
Wait for the Rebirth Egg to hatch. Raise the Chao however you want. As before, your actions will only influence the stats of the ultimate Chaos Chao.
Wait for the Chao to die again. It will leave another Rebirth Egg. The Chao in this egg will be capable of evolving into an Angel Chaos Chao, Devil Chaos Chao, or Light Chaos Chao.
Wait for the Rebirth Egg to hatch. Your actions during the child phase of this Chao will determine if it evolves into an ultimate Chaos Chao.
Give the Chao one of all 21 animals in the game. Do not give the Chao more than one of each animal or any Chao Drives.
Pet the Chao to alter its alignment. The alignment change depends on which character is used to pet the Chao. The Chao will move towards the Hero alignment when petted by Sonic, Tails, or Knuckles. The Chao will move towards the Dark alignment when petted by Shadow, Eggman, or Rouge. The alignment will determine into which form the Chao will evolve.
Wait for the Chao to evolve. It will evolve into the Angel Chaos Chao, Devil Chaos Chao, or Light Chaos Chao depending on the alignment.