I quite like the distinction that Formendacil makes between the demonic and the humanoid races of evil. One made an active choice; the others were born into it. I often find the un nuanced all bad villains boring, and have wondered why this never bothered me in LotR.
For me it is probably down to two passages in the books. The conflict between Ugluk and Grishnakh and the conversation between Shagrat and Gorbag.
The first quite clearly show us that these are not just mindless beasts, but that orcs have agendas of their own, and are in fact very much like humans.
Secondly, we have the conversation between Shagrat and Gorbag. In some way, it is one of the most important part of the books for me, as it portrays the orcs as having personal agendas and individual characteristics (that are not pure evil). Where Ugluk and to some extend Grishnakh seemed loyal to their demonic overlords, Shagrat and Gorbag seem to have much more of their own agenda. They question demonic authority and indicate desire to live in “peace” somewhere (with loot of course). That they end up slaughtering each other; probably show that they are beyond redemption, lest the reader start getting to much sympathy for them.