While Venom is one of Spider-Man’s greatest enemies, he at least lives by a code, but Carnage relishes chaos and slaughtering innocents, making him significantly more dangerous.
It was this baby symbiote that bonded with Kasady, turning him into Carnage.
In case you’re not familiar with Carnage’s comic book history, Cletus Kasady was already a psychopathic serial killer long before he shared a prison cell with Eddie Brock, but when the Venom symbiote broke into Ryker’s to bond with Eddie again and help him escape, it left behind an offspring.
Carnage is one of the many Spider-Man villains who hasn’t been adapted for film yet, but rather than pit him against Tom Holland’s iteration of the Web-Slinger, it appears that Carnage is being saved as solely a Venom opponent for the theatrical realm, which is fitting given how much the two hate each other in the source material.