Back when Once & Always came out, I posted this headcanon explanation regarding both Trini's death, Minh's initial inability to morph, and her inexplicable survival of the same attack from Rita that had killed her mother:
This is more my own headcanon than anything, but after thinking about all of the ranger deaths that involved fatal blasts and explosions, I like to think that it wasn't either the morpher or the grid that protected Minh, but rather Trini herself from within the Morphin Grid. When Zayto blew up at the end of Dino Fury, Master Red said that Zayto became one with the Morphin Grid, and his death was a lot like those of Kendrix and the Magna Defender. I like to think that not only did Kendrix and MD become one with the Grid, but that Trini did as well.
I also like to think that the reason Minh couldn't morph at first wasn't because the morpher or the Grid wouldn't let her (since past seasons have shown people with selfish or even evil intent being able to morph without any issue) but because Trini herself wouldn't let Minh morph. In both Lost Galaxy death cases, their morphing powers were passed onto their respective successors (Karone and Mike) only after Kendrix and MD first chose them and granted them access to their respective powers.
From within the Grid, Trini would have been observing Minh's behavior and would prevent her from using the morpher for vengeance, not choosing to pass on its power to Minh until she was truly ready, in both mind and body. And when Minh took the blast meant for Billy (the same blast that Trini took and died for Billy a year earlier), Trini's spirit within the Grid would have protected her just as Kendrix's spirit saved Karone when she nearly died after being sent off a cliff by Trakeena.
That rush of memories about Trini that Minh got from the morpher? I like to also think of that as the presence of Trini's spirit washing over Minh, comforting her daughter as if to hold her in her arms for one last time as a final goodbye, using the morpher as a means to connect Trini from within the Grid to her daughter in the physical world. And so with Minh having performed a heroic act of self-sacrifice that her mother's spirit kept her shielded during, Trini finally chose Minh to be her successor and at last allowed Minh to morph.
Since the release of Cosmic Fury, I've felt the need to revise this a bit as there were a few other Ranger deaths and resurrections I'd forgotten to take into account at the time.
While I do still think that when a ranger is killed when morphed (and thus when their connection to the Morphin Grid is at its most active), I no longer think that any ranger can eventually come back from the Grid on their own, which is what I previously believed about Kendrix and Zayto since I had misremembered Dino Fury saying that Zayto only came back because the Morphin Masters brought him back.
In Kendrix's case, I do believe that it was probably Master Green who brought her back, as her return seemed to just happen on its own independent of the Quasar Sabers undoing the curse Furio placed on Mirinoi's inhabitants way back in Lost Galaxy's second episode. Kendrix also seemed to be aware of the Galaxy Rangers' progress prior to her return, as when she reappeared on Mirinoi, she said to the others "I knew you'd make it here," as if she'd been watching them and waiting for them to arrive, which would mean her revival was set to happen even before the rangers ever reached Mirinoi. And, this is just a coincidence, but Kendrix's return was animated with a glowing aura that had a particularly
GREEN tint to it.
I had also forgotten about Steel's death, revival, and transformation into a human in the Beast Morphers finale, which Dino Fury also said was Master Green's doing.
A similar thing even happened to Mack back in Operation Overdrive's finale, but that case we know wasn't by a Morphin Master but instead by the power of the Corona Aurora. Being the "Crown of the Gods", it would stand to reason that its power is that of the gods and therefore on par with that of a Morphin Master at the very least (if not even greater than).
Gem and Gemma were also destroyed in the RPM finale, but it was shown that they were absorbed into the RPM Rangers' Bio-Field (which has since been confirmed to be the RPM Universe's name for the Morphin Grid) by Venjix when he took control of the Bio-Field, and it was shown that Dr. K brought them back from it with help from Tenaya planting a virus to disrupt Venjix's control over the Bio-Field, so no Morphin Master was needed to help with that.
Other rangers or ranger-like allies resurrected onscreen were Zhane, Daggeron, Leanbow, and Robo Knight.
- In Zhane's case, he temporarily flatlined and his revival was seen as nothing more than a medical miracle. But re-watching his revival, he comes out of his cryogenic chamber at full power, ready and rearing to kick butt. He wasn't even groggy or in need of any adjustment to being awake again. It's possible that Master Green not only restarted his heart but also restored him to full health.
- For Robo Knight, he inexplicably reappeared alive and well in the Extended Edition of the Legendary Battle, but since Dino Fury said that everyone coming to help the Megaforce Rangers in that battle was Master Green's doing, Robo Knight's return can be attributed to her as well.
- As for Leanbow and Daggeron, The Master seemingly killed them both by absorbing their good magic, but Necrolai used the last of her dark magic to revive them. By all appearances, this didn't seem to have anything to do with the Morphin Grid (since it wouldn't be until Operation Overdrive that it would be mentioned again for the first time since the Zordon Era) even when taking the later retcons into account. This makes their deaths and revivals seem kinda like outliers as I sincerely doubt Necrolai had any kind of power that could tap into the Morphin Grid and bring them back from it. I guess in this case, we just have to roll with the old saying "It's magic, it doesn't have to make sense" and not think too much about Daggeron and Leanbow's case.
One more cases I wish to explore is that of Alex from Time Force.
For Alex, he was struck down by Ransik while morphed, but then de-morphed and lived long enough to speak his final words to Jen while being held in her arms. He then appeared alive later in the series with the only explanation of "I barely survived Ransik's attack." While he also claims that the future was changing due to the activities of the Time Force Rangers in 2001, what we see of the future throughout the series doesn't seem to have really been affected at all, so I don't believe that his death was undone by changes to the timeline. Instead, I feel like his life was saved simply by Year 3000 medical technology, as when Alex seemingly died in Jen's arms, a team of medics ran to his side and looked like they were about to treat his injuries. And with Alex later confirming he "barely survived" the attack, "barely surviving" is still a form of surviving. So while he likely was dying at the time, the medics got to him quick enough to get him to a hospital and save him before he could fully perish. Jen and the others simply didn't know that Alex had been saved at the last minute.
As for what, then, Alex meant by the future being changed, he was likely talking about changes that would have happened had Frax's Dragontron robot defeated the rangers in 2001. Destroying Dragontron was the whole reason Alex came back in time in the first place, so the successful destruction of that robot prevented the future from being changed.
And as for any other rangers/morphed allies who have died but
not come back to life, if they were killed wile morphed, they're probably still in the Grid too. These would be the first Magna Defender, his son Zika, Sky's father from SPD, Jayden and Lauren's father from Samurai, the four other Rafkonian Rangers from Dino Fury, and of course Trini. The Grand Shogun from Super Samurai may have also been died in battle since he (like Kendrix, Zika, and the first Magna Defender) appeared as a Force Ghost to Jayden when he first acquired the Bullzord and Shogun Mode.
Meanwhile, if any rangers/morphed allies simply died from old age, they're probably just normal dead and not inside the Grid.