Well, Alduin is just the Nordic perspective of Akatosh, hes not really evil but they see him as the creator and destroyer of Nirn, who devours the world and leaves a new on in its place on regular intervals in his lifecylce, he is not the chief of the Nordic pantheon but its wellspring, albeit a grim and frightening one, also that since the Aedra were not made as good but a mix of good and evil, the Aedra as a whole may just be beginning to show thier side of evil... well really have to see just what dark secrets the gods hold for us ^_^