Ive tried... doesn't seem like you can, even if you go to a dark fortress, town, ect, random npc's tend to spawn either way... but I do know that kobolds are impossible to kill off since they just literally respawn as soon as u leave their area...
I even tried invading goblin civs, forcing them out of their fortress and pits into campgrounds.. and attempt to kill them all off (takes forever), but randomly on a rare occasion the game crashes upon attempting to load certain people (old vanilla raiding glitch as far as im aware of)
No, thats not how that works in dwarf fortress, populations are tracked. Its just that populations can be very big. And only a certain amount of them can be loaded at a time. There is no such thing as "respawning" in the normal sense in dwarf fortress, the only time respawning happened, it was a bug and was promptly fixed. Its more like "loading more entity population since the numbers are large".
You can easily confirm that i am correct by using legends viewer look at a place in legends viewer check its population, go to that place (a hamlet, kobold cave or whatever), kill a bunch of them. Retire, export legends, and look in legends viewer, you will see that population has now dropped. Or you can just depopulate a hamlet and see that they dont come back.
Even animal populations are tracked. I havent tested whether your kills effect wild animal populations in awhile, but i believe t is indeed the case and that it has been asked on the FOTF before. (Also i recall that i killed off the giant wolverine population on a mountain once, and confirmed with legends viewer) (they have small populations in each region, so are a good test case)
The only time "actual" respawning happens, is with Angels in Vaults.