Sonic the Hedgehog (Sonic Adventure 2)

Sonic the Hedgehog is fought in two boss battles in the Dark Story of Sonic Adventure 2. Both fights are done by Shadow the Hedgehog.

Battle
The first battle takes place in a square field on Prison Island, after Shadow clears White Jungle. Sonic will simply attack by jumping and performing the Homing Attack. Shadow has to hit him from behind when he is not jumping to hurt him. Three hits are required to defeat him.

The second battle takes place on an infinite straight track on the Space Colony ARK, after Shadow clears Final Chase. Here, Sonic is the final boss of the Dark story. Unlike before, Shadow must keep running to stay ahead of the falling platforms behind him. There are also meteors that will hurt Shadow when they explode. Like the previous battle, Sonic will mainly attack with the Homing Attack. His other actions depend on his position during the fight. If he falls behind or off the track, then he will use Chaos Control to warp in front of Shadow. If he gets too far ahead of Shadow, he will use his super move, the Sonic Wind. Five hits are nessesary to defeat Sonic.

Trivia

 * The fight against Sonic in the Dark story is very similar to the fight against Shadow in the Hero story.
 * If noticed during the first battle, Big the Cat can be seen below a vent.