Melkor's fears
Why is it that Melkor, who is arguably the most powerful of all the powers (except Eru of course), is afraid of the others? Particularly Tulkas and Manwe. He flees from Tulkas. He hates Ulmo and his vassals and never has power over them. He also shows fear towards Ungoliant, Eonwe, and also in small degrees, towards Feanor and Fingolfin. Is it separation from Iluvatar, or is it something else?