@Elder Mythos My main problem is that using "Demonic" doesn't take one thing into account: what about entities that in opposition to the sacred, but obviously not demonic? The average RPG setting is full of deities that use "evil" powers without anything to do with demons themselves, for examples.
Also, note that usually in animistic religions demons do have an opposite force: good spirits and good deities. Yeah, there is not a literal "anti-demon" kind of creature, but demons are in opposition to something. Note that I mean on a conceptual level, not on a lore-wise level: as in, maybe demons do not openly go against the forces of good, but common folk still perceive them as being in opposition to them.
That said, I'm curious. Why do you think "Demonic vs. Angelic" would be better than "Unholy vs. Holy"? It's just so hard for me to choose the former over the latter considering the points I brought up, so I would like to hear your stance.
@Elder Mythos Gnosticism is, as far as I remember, still an Abrahamitic religion; yes, its cosmology is not 1:1 with that of the Three Great Religions, but it's still a derivation of them. Don't know anything about Guanches religion, but I don't see any mention of angels in the Wikipedia page. Zoroastrism is the only religion that has an equivalent, and it's still an Asia Minor-born religion which, not-unrelatedly, is considered by many historians as the "ancestor" of Abrahamitic traditions.
To make it clear, I'm not saying that we must make a dissection of what exactly is a deity vs. a divinity vs. a demon vs. an angel vs. some other servant of the deity etc.. That's beyond the scope of a wiki who is mainly used for the Stand Generator and feat wars between fandoms, I believe. However, we should still try to present information as clear as possible. The problem is that you can't apply the word "angel" to most cultures or even fictional settings: drop the word in when talking about Buddhism, Mesopotamian, or really any Animistic religion, and people will look at you strange. The same doesn't happen when using the word "demon" because it's more general in definition, but than there's the problem that every other opposite of "demon" is, instead, too speciffic. "Holy" and "Unholy" have none of those issues, being both generic enough and a perfect dichotomy.
@Heartz13 Other than what @Baleyg Erebus just said, "Diabolical" is also not apt as a term because the "Diabolos" (the Devil) is a type of concept that is not found in every religion, and also tends to evoke specific Abrahamitic-like imagery as opposed to the more general "demon" and "fiend". Yes, technically "devil" is also a synonim of the two former words, but how many time will you find someone refer to a rakshasa or a Mayan plague spirit as a "devil" rather than a "demon"? Moreover, this has again the problem of excluding evil-embodying powers that are not specifically thought of as "fiendish": someone cursed by the gods may possess Unholy attributes without being necessarily associated with demons.
Personally, I would go with Holy-Unholy.
"Angelic" represents a concept that is too specific and does not translate well to non-Abrahamitic cosmologies (nobody would use the word "angel" to describe daevas, for example); "Demonic" (I would say "Fiendish" sounds better, though) does not have the same problem due to being much more general, but it's hard to use it in a dichotomy due to its opposites all having much more specific implications: "Heavenly" doesn't take into account positive powers that are not associated with an afterlife, "Celestial" powers not associated with the sky, etc.. There is also the issue that "Demonic" as a word evokes a particular concept of creature which may not apply to every "Good-opposing supernatural entities" within the same setting; for example, the Islamic Iblis is not associated with demons in some interpretations, despite clearly being in opposition with Allah.
On the contrary, "Holy" and "Unholy" are very malleable terms that are fitting for every kind of "positive/negative force" kind of entity. The only issue I see is that, within the same setting, different religions may deem "holy" and "unholy"... but in this instance we are using a different meaning of those words. Yes, the cult of Bhaal The World-Eater may deem angels unholy, but BTWE is still capital-U Unholy on a cosmological level and angels still capitale-H Holy on the same basis. Similarly, the Cult of the Forest may deem technology as unholy, but technology isn't Unholy in a cosmological sense (assuming this specific setting doesn't consider it so), even though Nature Spirits may be Holy within the same setting. "Holy" and "Unholy", when talked about as cosmological forces, are so much more than "this thing is bad for my religion and this other one good", they're something more rooted within the fabric of the universe itself.
Also, on whether or not "angels" and demons are divine... I think that kinds of depend on what you mean by "divine". It's literally discussing semantics, there's no other way around it. For example, taking Abrahamitic traditions as an example: if by "divine" you mean "explicitely classified as some rank of deity", then it's clearly a "No"; if you mean "whose nature is beyond that of other mortal or supernatural creatures", than they both are; if you mean "deeply tied to or imbued with the power of a deity", than only angels are divine, while demons are not. There is also the problem that "divine" as a concept isn't necessarily associated with an actual "Divinity", especially in fictional settings. There are also cases of deities with no divine power (take Greek nymphs, for example). I think the best thing in this case is to refer to the setting itself, and whether it uses "divine" in a loose sense or is more specific in differentiating between the power of a deity and lower classes of beings.