This was such a great post X, thanks!
I however disagree with one minor point:
Personally I don't feel that Cloud cherishes his memories of Sephiroth, or at least ACC doesn't tell me that story. What he says is that there's nothing he doesn't cherish, sure, but we know what he's referring to at that moment, it's shown to us: Tifa, Marlene and Denzel, Aerith, Zack. These are the most important people to him and he cherishes them all, for different reasons, but they're all precious to him. And he wouldn't want to give up on any of them.
Such is not the case of Sephiroth. Tifa even refers to him when she says "is it a memory or us?", and this is why Cloud tells Sephiroth to stay in his memories: because he doesn't want to see him resurfacing in the real world. He doesn't want to follow Sephiroth's path, he wants to follow his own path, with his little family, he wants to live his happy life. Tifa's scolding, for all the bad reps it gets in fandom, was really helpful to Cloud as it was the push he needed to act.
Sure thing!
I'd like to position a number of details around that which might change how you look at the story in
Advent Children then, but also do so by saying that there is still a way in which how
you see the story still works perfectly in conjunction with what I said about it that I'll address at the very end to hopefully provide some other context to why our two VERY opposing perspectives aren't necessarily in disagreement at all, and expand upon why that's nuance that's a very difficult to pin down without a lot of surrounding context to frame what points about that scene that I think we're both looking at.
This is something that I've only started to think about in more detail post-
Remake, and it has to do with how Sephiroth answers that by refusing to become just a memory and how in
Remake he's constantly longing for a connection with Cloud because it provides him a sense of validation of being needed. This parallels the way that a lot of the classic Japanese rivalries are told where the emotion between the antagonists start from a position of utmost respect and fall into the antithesis of that, and what those bonds look like when that conflict is finally & truly resolved.
Sephiroth starts out as Cloud's literal hero. The person he is inspired to become like, so that he can save all of his friends and protect everyone. Prior to
Remake, in
Kingdom Hearts 2, the conflict between Cloud & Sephiroth is laid out fairly overtly with everyone in their
Advent Children attire, explicitly stating that it's Cloud's refusal to let go of the darkness from his past that keeps calling Sephiroth back, and Cloud's stabilized by having the light of the bonds of the people around him to help balance himself out. That's something that Sephiroth didn't have.
In a sort of Yin/Yang relationship, Cloud is this little spark of light that Sephiroth refuses to be without, and Sephiroth is this little pool of darkness that Cloud refuses to let go of. Their trauma & experiences are mirrors to one another that just amplify and reinforce that bond. That's central to much of the Deva-Asura conflict in the nature of the two conflicting forces of the universe in Buddhism, much of which informs how those stories were portrayed in Shura Noh and other works since.
This is why in things like Dissidia, Cloud is in the form of a warrior of Chaos and on the same side as Sephiroth, and also why he eventually forms himself into an identical opposition of Sephiroth. It's an ebb & flow of that cycle.
This also brings to how Sephiroth's parting words with Cloud in Dissidia NT are,
"Evenutally, our goals will align. And when they do, we shall meet once again." and then the next time Sephiroth appears was in Remake with a belt design heavily reminiscent of his Dissidia designs.
This follows through into the nature of how Sephiroth is portrayed as being the antagonist to Cloud in
Remake, Sephiroth is constantly goading Cloud forward and talking about how he won't be strong enough to stop it from happening again. At the Edge of Creation he's attempting to team up with Cloud, and has this protective way with what he does that slowly turns Cloud into himself. The point is that, as two sides of the same coin, Cloud's own sense of self has the same effect – and that's something that's important when it comes to understanding the mechanics of PTSD specifically.
There's a very unique type of attraction & repulsion that happens with this sort of rivalry that has its formation in PTSD, but especially when it involves visual hallucinations of the person who caused the trauma. The brain's survival mechanisms boils down to an "Us vs. Them" analysis, because that's how we start out – as an interconnected organism to our mothers. The mother's brain rewires during pregnancy to recognize the infant the same as she recognizes herself, such that her own survival instincts will extend to the child. This is what forms the foundation of social bonds, it's why infants don't display survival stress signals when their guardians are present, and how they are able to learn more about the world around them rather than operating out of instinctive fear. There are a number of studies that look at how children that display a lot of precocious developments are often the result of not having those things and their bodies needing to age rapidly to care for themselves. This is why the "genius" type has a very heavy overlap with that type of elite loner character in Japanese media as a juxtaposition to the outsider who still desperately craves connection as the two different reflections of those coping mechanisms. (See: both Sephiroth & Cloud following the same archetypes as character rivalries that are overtly in Indra-Asura pairs like Sasuke & Naruto where Naruto gets very overt about that, as well as Yasha & Asura in
Asura's Wrath as a more direct adaptation of those Buddhist & Hindu narratives that form the underlying religious & spiritual core to how those stories started to be told in Japan using the Asura Realm in Shura Noh).
This fundamental survival mechanism is why babies literally don't recognize themselves as distinct entities from their mothers until later in cognitive development, and this plays heavily into how the biological elements with Jenova (inspired heavily from John Carpenter's alien in
The Thing) are intertwined into the non-dual relationship between Sephiroth & Jenova (which extends very heavily into a lot of other Japanese exploration of Lovecraftian alien horrors around those themes with Eve in
Parasite Eve and also things like the Great Ones in
Bloodborne). There's always an exploration of this sense of both isolation, but also in losing who you are when you're fundamentally a part of someone else in individuals who struggle to connect with others socially, which is why having social bonds is ALWAYS a core element to overcoming that – because we literally do not have the power to do something like this without other people, and our social connections to one another. This is also why the conflict is typically something that fundamentally damages the ability for those to form or be stabilized as the catalyzing trauma at the heart of those characters, and they're faced against some form of a coping mechanism that's spiraling out of control and overtaking everything else.
What happens in trauma is that the Amygdala responds to similar stimuli and massively amplifies that bias as a survival reflex, (this is why Cloud's moments of trauma & hallucinations most often get triggered around collapsing bridges in both
Remake &
Rebirth), the more you continue to experience those things over & over, the more heavily that bias will define the "other" as everything that is antithetical to you & reinforce the need to protect itself during those times, and just becomes a feedback loop that spirals out of control without assistance and intervention. If you're weak – it's strong, if you're human – it's alien, if you're moral – it's unkillable, basically it's just amplifying the "Us vs. Them" to extreme degrees and polluting your sensory information with those memories to the point that triggers cause visual hallucinations of the individual who you associate with the trauma.
What's counter-intuitive is that you can't defeat something like that. Anywhere that Cloud's around people he cares for, that fear gets amplified, he feels helpless, and like clockwork – Sephiroth eventually shows back up again. This is true of real world PTSD hallucinations as they are most common when someone is in a place where they're meant to feel safe, with
a lot of the research that Jonathan Shay did back in 1995 with Vietnam veterans showing that they often experienced them at things like Christmas, birthdays, and other celebrations. What ends up being the solution to this is to remember that the people in those horrific circumstances were
JUST LIKE YOU. They're just as human, went through all sorts of things, and hit a breaking point that shows just how easily you could have been in opposite positions, and just how little there is that ACTUALLY separates the "Us vs. Them" that feels insurmountable to your brain when it's in a survival state. Accepting and understanding that fundamentally undermines all of the ways in which the "other" is "alien, all-powerful unstoppable, unkillable, etc." and makes them just a memory to you. That's ACTUALLY what's done in therapy with PTSD victims that's effective in stopping those sorts of visual hallucinations that Cloud experiences with Sephiroth is in seeing them not as a hated enemy, but literally as an honored guest.
That's the exact resolution that causes Kadaj & the other Remnants to be embraced by the Planet and finally be at peace. If you look at how the stories of those rivals get portrayed in Japanese media as a reflection of the Hindu/Buddhist reflection of those values of the Indra-Asura / Deva-Asura conflict & cycle,
they resolve that way. They recognize that the more they stood against each other, the easier and more undeniable it became to see how they were similar, and could have been in one another's position with the tiniest difference in circumstances, and it's in giving up the hatred and learning to cherish the other person despite the need to stand against them when their coping mechanism was existentially destructive to others around them. That's why the lingering trauma being unresolved in Sephiroth is his refusal to submit to merely being Cloud's memory, but Cloud's ability to move on is understanding how even those painful memories are things that he can cherish.
This is why Tifa's question of,
"Is it a memory, or us?" is in framing what Cloud is allowing to control his life, and it's in having the support of others that enables Cloud to not be overwhelmed by the pain of those darker memories. Stress is clinically the lack of control, and a lot of stress adaptation disorders are about being stuck with a lack of control that amplifies that PTSD. So, instead being controlled by those stimuli that trigger your brain to respond automatically, you need others to help disassociate those fears and reflexive coping mechanisms to allow you to be back in control, which then allows your brain to relax and stop pushing itself into a survival state any time something feels similar to a particularly painful memory. If you cherish the moments that are the most terrifying, you have an ability to take agency over them.
That's also the thing that Sephiroth doesn't have and continually refuses, even as the Remnants embrace being welcomed by the Planet which was once their most hated enemy. It's the survival instinct of Jenova that causes her to reject death and reassemble her cellular material in a constant cycle of death & rebirth, rather than to return to the Planet and fade into memory – she is by her nature as a calamity that crashes into and scars the Planet itself a representation of that type of survival trauma & the conflict that comes about as a result of it. As Sephiroth represents that, he remains committedly antithetical to that solution even as Cloud is able to smile again in the end despite knowing everything that Sephiroth took, he's not controlled by guilt and is able to live in the present with those he cares for because everything else stays in his memories where it belongs –
EVEN SEPHIROTH.
That's why
Advent Children is more of a definitive end to Cloud's trauma with Sephiroth. That's what enables him to show up to aid Vincent in
Dirge of Cerberus and be a pillar of strength, because that's over now and he knows how to live with those things and cherish them. When he isn't strong he always has the others around him. This is echoed all of the
Kingdom Hearts 2 themes in why Tifa is the light that helps Cloud push back Sephiroth, and in the how/why for this cycle in
Remake where you can look at it both as being sequential to the original game as well as a retelling of the original. Trauma is cyclical, and so revisiting and looking at these things from a different perspective is where I've found the most value from the
Remake project as it's helped in contextualizing a lot of choices that the stories make, and also let me study & learn a lot of things about them in the process.
All of the stories in
Final Fantasy VII follow this with differences based on who the various parties are and what they struggle with, and there's a lot of spiritual and philosophical difference to how those opposing forces are portrayed that differ a lot between how the protagonist & antagonists of most Western literature & contemporary media portray those differences.
To get to how you saw the story in your reply, there's a lot in here about the cultural differences in the Deva-Asura conflict in Eastern cultures in juxtaposition to the God vs. Satan conflict in a lot of the Western world that represent
VERY fundamentally different things when talking about Light & Darkness. This means that when following those religious/spiritual/philosophical perspectives, Eastern conflicts the "Good vs Evil" are two sides of the same coin where minor nuances in moral justification can instantly turn one side into the other and it is fundamentally impossible to remove one without the destruction of the self, whereas Western conflicts the "Good vs Evil" are more about "tolerance & intolerance" where it is impossible for one to exist safely without the eradication of the other.
Looking at the portrayal of Holy & Meteor in Final Fantasy VII in those two contradictory lenses is actually what first got me digging more deeply into the nuances about the spiritualism, philosophy, and narrative history that form the foundation of these sorts of stories in Japanese media, so there's a lot of tl;dr that I'm trying to skim through and still touch on in how those align to what we've learned about those sorts of stress adaptation disorders from a clinical perspective as both are deeply fundamental to how & why things are portrayed in a particular way. Holy defensively eliminates anything that is a threat to the Planet, and Aerith states that it's a materia that doesn't do anything, and Cloud tells her that she just doesn't know how to use it. Holy's intolerance for Jenova because it views it as a threat creates the same underlying dynamic that leads to Geostigma in Advent Children. It's like an auto-immune response that's overcompensating and damaging the body, and similar to how the Weapons end up protecting Sephiroth by turning against Shinra, most of the narrative focuses on how those cyclical traumatic cycles will reinforce things into more and more destructive ends.
At the same time, the Planet can't survive without forcing Shinra's exploitation to stop. What's important here is that Cloud & Sephiroth are both aligned against Shinra and want to bring it to and end. The difference is whether or not Sephiroth rebuilding the future in his own image is something that can be seen as justice or intolerance. He refuses to tolerate the humans torturing his mother and usurping THEIR Planet, and if you embrace that perspective you see how easy it is to take his side, but that also embraces his utilization of intolerance where he is essentially not difference from Shinra creating a Promised Land for themselves through the exploitation of others. Conceptually this is something that Cloud NEVER embraces so long as he has agency to be able to define himself as someone who isn't Sephiroth. That's not something that falls into the category of what's being cherished, and when you view Sephiroth as the undying manifestation of that intolerance refusing to submit I would agree that it's something that
isn't cherished by Cloud in the end.
What IS cherished is the person Sephiroth was to him despite their conflict. The motivation to be stronger for the people he loved no matter what, the image of the hero he pretended to be until he actually WAS a hero to those he loved. As more and more of Young Sephiroth's story gets told, it's clear that the things about Sephiroth that Cloud cherishes are the same parts of Sephiroth that he lost & gave up to cling desperately to survival in the same way that Jenova did. It's putting
THAT to rest which can be interpreted in either way when you look at different parts of that story even though they're all interwoven together.
Thus my main reason for that critical distinction is one that's primarily rooted in how the story looks at the spritual & mental health elements of how those are portrayed and how we treasure things that were painful (given the thread around mental health with Sephiroth specifically and how he and Cloud are a lens into one another's trauma cycles), and in that context it's less about the existential social contracts to the concepts that we embrace around tolerance & intolerance who we are as a result of that. Essentially Cloud positions himself to always keep a hold of Sephiroth in a way that fundamentally disarms him and doesn't allow that intolerance to gain a foothold. That's why it's Tifa who becomes the catalyst for Cloud to act
RATHER than Sephiroth in
Advent Children &
KH2, even though Cloud doesn't let go of those dark memories of his past –
he doesn't need to because she's there to support him through that struggle, and he's no longer ruled by the fear of what happens if he fails like he was by the memories of Aerith & Zack, because they're still there with him as his memories to help carry and motivate him just like Sephiroth did. He's gonna be ok, because he was able to come to terms with what happened and decouple himself from that old coping mechanism that ruled him through trauma & rejection of pain.
X 
