Amy Combo card:

Enter alogK as a password in Emerl's story line at the Sonic Team Building.

Chaos Combo card:

Enter EkiTa as a password in Emerl's story line at the Sonic Team Building.

Cream Combo card:

Enter ZAhan as a password in Emerl's story line at the Sonic Team Building.

E-102 combo card:

Enter tSueT as a password in Emerl's story line at the Sonic Team Building.

Knuckles Combo card:

Enter yU3Da as a password in Emerl's story line at the Sonic Team Building.

Rouge Combo card:

Enter AhnVo as a password in Emerl's story line at the Sonic Team Building.

Shadow Combo card:

Enter ArmIa as a password in Emerl's story line at the Sonic Team Building.

Sonic Combo card:

Enter 75619 as a password in Emerl's story line at the Sonic Team Building.

Tails Combo card:

Enter OTrOI as a password in Emerl's story line at the Sonic Team Building.

Hint: One-hit KO:

Get your green bar full either by powering up using L, or by blocking attacks. When your bar is full and your character starts flashing, press R. If the attack was successful, your opponent/opponents will die.