Carnage Cosmic:
In the "Absolute Carnage" storyline, Carnage merged with the Grendel Symbiote, becoming a powerful cosmic being known as Carnage Cosmic. He possessed immense power, including the ability to manipulate cosmic energy, create constructs, and control vast armies of symbiotes.
Venomized Carnage:
In the "Venomized" event, Carnage was bonded to a portion of the Venom Symbiote, creating a "Venomized Carnage." This fusion temporarily gave Carnage enhanced abilities and a more monstrous appearance.
Rexelent:
In the pages of "Venom: First Host," Eddie Brock and Carnage are brought together to form a new entity called "Rexelent." This composite being possesses the physical strength of Carnage and the telepathic abilities of Eddie Brock.
It's worth noting that these fusions are often temporary, and the merged entities eventually separate into their individual components.