Quasqueton said:
The demon lords and archdevils are CR ~25, yes?
Using the 3e stats yeah, but keep in mind that these are the same beings with a long history of being on par with true deities, and exceeding the power of true deities in some ways when on their home plane, and some of them are in fact deities (or were before all of them were retroactively made into 'level bosses' for PCs to beat up and loot).
By 3e stats a weak deity could smack around the most powerful archfiends (Demogorgon, Mydianchlarus, Asmodeus, etc) but Asmodeus exiled the Orcish and Goblinoid pentheons from Baator, the fiends collectively force any non fiend deities from having any active roll in the Blood War, the yugoloths carved a 40 mile+ tower from the spinal column of a deity they killed, Prince Levistus of Baator was slowly winning a war against both Sekolah and Set (both of them true deities), etc. The 3e stats do not reflect their history and flavor. And when history and flavor run up against watered down and inappropriate stats, I'm willing to sacrifice the stats on the altar of quality control.
For the most part it's a standoff between archfiends and true deities, and they largely avoid the affairs of the other. Gods have a devotion to the prime material and their worshippers and their portfolios while archfiends will have older, more base desires of the promotion of their alignment and their own personal power in their home plane, and they'll be less concernd with the prime material. A true deity is largely unquestioned within their own deific domain but outside of those domains the archfiends control the utter bulk of those planes/layers of planes of the lower planes.
Under the right circumstances a deity might kill an archfiend assuming they're willing to live with the consequenes of other fiends going after them and other deities going after them for upsetting the status quo. But also by the same token an archfiend might likewise go after a true deity. I've had an instance in my own campaign of an archfiend getting into a direct conflict with the avatars of two deities and it ended rather poorly for the avatars in the end, though the fiend had some wind taken out of its sails by the experience and made an exit back to its home plane almost immediately thereafter to avoid any larger scale retribution that it wouldn't be capable of withstanding.
