Is it possible to cause an undead to just become dead without destroying or killing it? The magic that creates an undead are instantaneous (except for special case skeletal crew and possibly others, but focus is on create undead and animate dead) so dispel magic and antimagic field have no effect.
Say someone on the side of good wanted to free the body of someone that was turned into undead, say a loved one, member of their faith, .... Is there anyway for them to do so?
I found a single spell which affects zombies, which at the end turns them back into un-animated corpses.
So well its not everything that I was hoping for, it does mean that zombies can be reused if I make some.
The spell is flesh wall, and is cleric/wizard 6, so I wont be doing it soon.
You can use zombies already under your control as the material components for a flesh wall. However, they and any other corpses in the wall revert back to inanimate corpses when the spell ends.
I searched through many spells, magic items and monster special abilities, yet, the only way to make a soul depart from the body also mentions the words killing, slaying, or destroying. The only thing that you could remotely do is to transfer souls into the undead's body, suicide, and come back to your body. Their soul is lost having no body to return to, but the creature still got slain.
If the host body is slain, you return to the magic jar, if within range, and the life force of the host departs (it is dead). If the host body is slain beyond the range of the spell, both you and the host die. Any life force with nowhere to go is treated as slain.
So, if your purpose is simply to not let them feel any pain or violence, this is the most humane way to get them to rest.
If the thing that caused the undead to arise in the first place counts as a curse, which includes but is not limited to any spell with the [curse] descriptor, and the source is not a spell of higher than 5th level, the spell Break Enchantment can undo it, being able to undo even instantaneous effects provided they are enchantments, transmutations, or curses. Enchantments and transmutations are defined things in the rules, but curses aren't.
You can also do this if the specific kind of undeath involved involves paralysis-- via Primal Scream and scrolls and Command Undead or diplomacy skill checks-- but that is both more complicated and less useful, generally speaking.
Beyond that, there's time travel via the Scepter of Ages, perhaps acquired via Black Market Connections. There's also Polymorph any Object which would allow you to turn a e.g. a zombie into a corpse permanently. There's also stealing the soul out of an undead target, via Trap the Soul or any more specialized lower level method. One may also be able to use Freedom or Freedom of Movement to render a soul free to return for the purposes of Clone et al. Resurrection and True Resurrection also work when cast on an undead creature: while the spells themselves say nothing beyond being able to raise undead creatures that have been destroyed, the description of the Undead type specifies that 'Resurrection and true resurrection can affect undead creatures. These spells turn undead creatures back into the living creatures they were before becoming undead.' Undead creatures that are turned back into living creatures won't be dead, though, so they'll still need to be corpsified via some other method to achieve de-animation. The Promethean corruption also incrementally transmits a creature's soul to the afterlife, eventually resulting in a mindless destructive automaton or free-willed evil construct, but one that doesn't have the original creature's soul. Killing this new creature is sufficient to deanimate the corpse, but the original creature will be basically impossible to raise from the dead at that point due to the other effects of the affliction.
There are probably other ways. What you are asking for are weird edge cases where something ceases to be alive (or unalive) without technically dying or being destroyed, and there's lots of unrelated weird edge cases in Pathfinder.
Destroying an undead doesn't necessarily mean destroying its body. My first thought was undeath to death, which simply removes the animating force without doing damage. Then the body is free and in whatever condition the undead kept it in, at least. Unless it was a careful and vain undead, it's probably still in bad shape, but better than if you had to beat the creature to re-death first, anyway.
https://www.d20pfsrd.com/magic/all-spells/u/undeath-to-death/
