Abyssals, Sirens, and the origins of fictional naval enemies

Which are the least intelligent enemies: Kantai Collection's Abyssals, Azur Lane's Sirens, or the alien species of Warhammer 40K?

There is no agreed ranking. The replies describe Abyssals as products of human fear, Sirens as human-built machines preparing people for a future threat, and Warhammer species as more complex than their caricatures.

Kantai Collection's Abyssals are described as human fears of the sea, wartime deaths, and atrocities given form. They are presented as products of the human psyche alongside ship girls. Azur Lane's Sirens are also said to originate with humanity: machines created in the future and sent back to prepare people for another threat. The panel disagrees over whether they are defective, while one response maintains that they still fulfil their original purpose. Warhammer 40K species are judged more interesting when examined beyond their caricatures, and more intelligent Orks are treated as a dangerous prospect. The Necrons' expanded background after fifth edition is praised for giving them personalities and history. Their distress at losing biological bodies is also discussed as part of their portrayal.