Re: CoM Enemy Cards?
You must be sure that you break multiple cards, or that's how I did it, and your enemies cards must be strong, nothing too small, that's why almighty darkness works well. Also be sure to go back to each world with Treasure Cards to get cards like Roxas and Xemnas.
World Rewards Cards:
I found Xemnas in World 3,which was Wonderland for me, he blocks out enemy combination's after the enemies second blow. Meaning the first hit is the only one that does any damage. This effect lasts for 3 Reloads.
Roxas was in Twilight Town, his card doubles your attack power for each attack card for 20 attacks.
I found Luxord on the Destiny Islands, he allows you to break enemy cards with any card, EX:your enemy throws out a 9, you play a 1 card and it is able to break it.
I found Xaldin in Monstro Floor 4, whenever your hit for three hit, you do Aero damage to your enemies.
You can also get Zexion from a Calm Bounty in Destiny Islands.
Tip for Key To Rewards: Keep killling enemies in Castle Oblivion Level 13, you're more likely to find them there than anywhere.