... Black and Green, right? :-) "... Marduk became more and more important until it was possible for the author of the Babylonian Epic of Creation to maintain that not only was Marduk king of all the gods but that many of the latter were no more than aspects of his persona - hence the Hymn of the Fifty Names of Marduk..." They also mention the spade (although it wasn't taken from another god) and the snake-dragon (adopted from Tishpak).

To return to your original point, there's no evidence here of the ritual slaying of one Mesopotamian god by another. Marduk may have assimilated some other deities, but major gods like Ishtar were still going strong during his ascendancy, with separate cults.