[Lord of Angmar]

And without demanding from readers an active effort to discriminate who is good and who is evil. (Bethberry)

I agree that Tolkien is not ambiguous in his characterizations. However, there are some examples that differ. There are varying opinions on the morality of such characters as Feanor and his sons and Turin Turambar. And certainly he leaves us in suspense until the end of the Two Towers about whether Gollum will change or remain the same. However, he does usually provide a clear-cut view of character morality as he defines it.