Carnage vs Cardcaptors just imagine one beautiful day in Tomoeda ( Sakura's Hometown) and then appears the red nightmare himself: Carnage. He came to this town to lure Venom through destroying it, and torturing people. Sakura and her friends appear to face him, but even though she can control everything, Carnage, that has the ability to see from every part from his body, avoids being attacked by the clow cards.
Even though Carnage is winning, Venom shows up just in time to help the cardcaptors.
After a crushing battle with Carnage, Venom temporally transfer his symbiote to a wounded Sakura so she could fight Carnage easier, and beat him. After being wounded by Sakura with Venom-suit, Carnage flees just to lead his enemies to a deadly trap. Sakura, Syaoran, Meiling, Keroberos, Yue, and Venom (Now rebonded with his symbiote) arrives where Carnage is, just to see that he has a extremely powerful sonic blaster, which he got from Alistair Smythe, and he's about to use it kill all of them with it.
He activate the blaster to its maximum power, and shoots a very strong sonic attack. Fortunately Sakura use her mirror card just in to reflect the sonics back to Carnage. Because it cannot stand against intense sound, the Carnage symbiote leaves Kasady, but promise him the it will back to him to get their revenge.
Even though Carnage loses in this battle, the cardcaptors must have been experimented the real madness through fighting Carnage.