This is up to your DM
(Note: this answer reiterates content from this answer which is for an overlapping question. It compiles findings from several related questions, answers and discussions, in an attempt to summarize.)
There are several spells to recall the soul and reunite it with the dead body of the creature it belonged to: Revivify, Raise Dead, Reincarnate, Resurrection, True Resurrection and Wish. They all differ slightly but (with the exception of Wish) share language that the soul must be free and willing to return, and there is also a general statement on p.24 DMG that a soul cannot be returned to life if it does not wish to be.
For the rest of this answer, we assume willingness. It is highly likely that a soul being tormented in Hades wants to escape and return to life. Moreover, in case it is the soul of a player character whose player wants to continue playing the character then we can assume the soul wants to return. If not, the soul cannot be reunited with the body, and the story ends here.
So the only question we need to answer is: is the soul free to return?
Released in Hades
The duration of how long the released soul will stick around before being used is DM territory. Is it free to be resurrected during this time?
The consensus says this is not clearly defined, and hence up to the DM.
There is no limitiation for Hades as a plane that would treat the souls there as trapped (as possibly would be the case in Carceri). From this perspective, they are free to be resurrected and it would be up to the DM to rule the soul used by a Night Hag or its customers for trading or experiments is stored in a way that keeps it trapped. The party, to resurrect their friend, would need to
- travel to Hades (via Plane Shift or similar means), and free the soul from its prison
- contact the Night Hag or the soul's current owner and negotiate terms for release
If the released soul would be a manifested soul i.e. and insubstantial shade that is the soul, we have precedent from the Specter. The text on Specter states such a form can exist (MM p. 279: "A specter is the angry, unfettered spirit of a humanoid that has been prevented from passing to the afterlife. (...) Some are spawned when dark magic or the touch of a wraith rips a soul from a living body.)" If so, it is accepted it can be recalled and brought back to life.
Made into a Larva
It is not clear if souls in Hades are immediately transformed into larvae, or if there is a time -- up to forever -- during which they remain insubstantial shades. This would be up to the DM.
According the the DMG, souls in Hades mortal souls take the form of insubstantial shades (Greek cosmology, p. 44), and Hades is the destination of many souls that are unclaimed (...). These souls become larvae (p. 63). It is unclear if only some souls become larvae, as in earlier editions), or all do. The wording on p. 63 suggests all do, the shades on p. 44 contradict it.
I think this is a cosmology-building decision left to the DM.
Does the form of the larva impose entrapment?
It also is not clear if the fact that the larva is an actual, living creature would block it from being resurrected. The text of most reanimation spells requires touching a "dead creature". So this comes down to answering the question:
What is a dead creature?
There is no consensus if the dead creature refers to the corpse of the former creature (now an object, technically speaking), because this is what you can touch, of if it refers to the combination of body and departed soul.
- If it refers to the corpse, then the status of the soul is immaterial and it can be recalled.
- If it refers to the combination of departed soul and corpse one can argue that both parts need to be dead for the overall creature to be dead (if a soul could ever be dead). Since the larva is alive, the overall creature then could not be target of a spell that cares about the creature being dead. Revivify stills work in this case, because it only requires a "creature that has died", not a "dead creature", and die they certainly did when the soul departed. But it has such a short window of time, it is highly unlikely that it matters.
It also is unclear if Larvae are manifested souls, or if they are new creatures composed of body and soul. There is language in the DMG supporting both views. For the purpose of resurrection it is not important, important is only if the soul is alive or not, in case one follows the argument that original body and soul make up the creature.
In conclusion, there is neither clear language nor consensus if it would be possible to resurrect a creature whose soul has been turned into a larva. So, this is up to the DM to rule.
Killed in Hades
What happens if the soul as an insubstantial shade (similar to a Specter) gets destroyed? We do not have consensus answers to guide us yet. This is up to the DM.
Hades is crawling with larvae. Night hags, liches, and rakshasas harvest them for use in vile rituals. Other fiends like to feed on them.
Lastly, once a Larva and harvested for use or fed upon, is it destroyed forever, or does this free the soul to be resurrected?
There is consensus that larvae are native to the plane of Hades. There also is precedent both for demons, and devils (the denizens of other lower planes) that they are utterly destroyed when they die on their native plane:
The only way to truly destroy a demon is to seek it in the Abyss and kill it there. (MM p.51)
Devils that die in the Nine Hells are destroyed forever. (MM p. 67).
Do these examples mean that if a Larva dies in Hades, it also would be truly destroyed? There is no explicit language about it for Hades, so in the end it is up to the DM.
For most points we are not able to establish clear answers from the Rules as Written and published lore, so they comes down to DM to adjucate.