Well I do think by the definition of one being retarded that Angron fit it perfectly, his tactics, plans, and processing of information was drastically below that of all his brothers and below that of the humans that served him (such as the ship captain, and some of his astartes).
Angron was unable to recognize or process that his tactics were inefficient, additionally he was unable to understand and process abstract forms of thinking. Particularly when he was recalling his fight with Russ and the wolves, Lorgar tells him that he is a foolish being for being unable to even see that he lost that fight entirely. Yet all Angron could reconigze due to his diminished mental processes, was that "Oh I punched russ more and he was on the ground longer". He was never able to see the tactics russ used, as well as that at any moment during that fight Russ could have killed him. Lorgar confirmed this, additionally Angron believed his forces kill more wolves yet Lorgar states that from every other source he knew, that it was the wolves who won the ground war too.
Angron is just unable to mentally see things beyond simple configurations, he is unable to process anything in regards to quantitative or abstract thinking.
Angron often times is depicted in both behavior, and thinking as a child. The body of a warrior with the mind of s stunted child stuck forever in childhood. He ruminates upon the same emotionally ques constantly, never able to even understand why he does so and why it bothers him.
Angron, the retarded child of the primarchs.
Last edited by Lux; 05-23-13 at 05:27 PM.