Dr. Eggman

Dr. Ivo Robotnik, usually called Dr. Eggman, is the main villain in the Sonic the Hedgehog series of games. He is Sonic the Hedgehog's archnemesis, but has occasionally teamed up with him.

Chaos
In Sonic Adventure, Dr. Ivo Robotnik found Chaos 0 and went to obtain the Chaos Emeralds to power up Chaos so that he could destroy Station Square. Eventually,He found all seven Chaos Emeralds and gave them to Chaos turning him into Perfect Chaos

The ARK
In Sonic Adventure 2, he entered a top secret government base to find Shadow the Hedgehog. Shadow the Hedgehog told him of a space station,the ARK, that had a weapon,called the Eclipse Cannon,which was so powerful that it could destroy stars.The only problem is that it needed power from the Chaos Emeralds. Later, He got them and put them in it, but he noticed that he had done something wrong and helped Sonic deactivate the cannon.

Trivia

 * Dr. Robotnik is often called Eggman by Sonic.
 * He apparently likes Chaos, as he has a Chao Garden on his ship, the Egg Carrier, and has a room full of them in his castle.
 * He has an IQ of over 300