[Tuor of Gondolin]

One of Tolkien's nice touches is the way he leaves open possible
speculative musings on various characters and events,
and why some early critics missed the shadings of some of
his characters. One can imagine scenarios where Grima is
redeemed. Note that both Theoden and Frodo consider him
worthy ofof being offered chances to choose redemption.
And it's a nice touch by JRRT to leave the question of Grima's
cannibalism not definitively answered (although I'm inclined to think he
probably was guilty, but even so, to what extent would that have
really been his choice, or did Saruman unduly influence and
dominate him)? But of course, one could counter by quoting
Tolkien. I think in one of the Letters he says something to the
effect of Gollum being the sort of wretched creature he was
because of earlier choices he had made.