So I'll try to make it short: In Tatsuya's Scenario in the Eternal Punishment PSP remake, there's a way to determine this scaling chain, and it's via the Kadath Mandala.
To keep it brief, here's what the translation said about it:
"There may still be a way though: the fragments of Shiori's self are scattered throughout the domain of collective unconscious known as
Kadath Mandala, the place where Personae and demons sleep and the uppermost domain of the abyss Philemon and the Crawling Chaos inhabit. Tatsuya's other self, his Persona, also comes from Kadath or, in other words, the place where the image of the gods from legends is born. Persona users of old who understood the power of their dreams and could visit the world of the collective unconscious also called it the domain of visions."
The Kadath Mandala is basically the furthest region of the Collective Unconsciousness, where Philemon and Nyarlathotep truly lie in. Compared to the normal CU, this place is much more dangerous. Igor says that this place was filled with Shadows and Demons thanks to the Faceless God, also known as Nyarly. Why do I assume that the Kadath Mandala is a separate realm that require more power than entering the regular CU? Well remember that way back Innocent Sin,
Tatsuya already entered the CU. So this means Kadath is an even further realm.
So what's so important about this place? Well first of all, you cannot just enter this realm, unlike the normal Collective Unconsciousness or the Sea of Souls. Igor explains that while Tatsuya has immense talent as a Persona user, he cannot open a portal to enter Kadath Mandala. Remember, this is already after Innocent Sin, so we know Tatsuya can enter the regular Collective Unconsciousness. But not the Kadath Mandala. So to aid this, Igor calls upon Chandraputra, who is actually the legendary Persona User known as Randolph Carter. He ended up like this after the Faceless God ripped out his mind and soul and placed it on an alien body. Chandraputra is a legendary Persona User who holds the Silver Key that allows passage through the Ultimate Gate to the world of subconscious, Kadath Mandala, and that Silver Key is what helps the P2EP gang to enter Kadath Mandala.
Now, what's interesting here is what Igor said. He said that Tatsuya Suou, being already a massively talented and experienced Persona user since Innocent Sin, couldn't hold a candle to Maki Sonomura. Why? Well with her strong will alone, Igor said that Maki can enter Kadath without using the Silver Key. The only Persona users powerful enough to enter Kadath are Maki and Randolph. Now wait, why are we assuming Maki is stronger than Tatsuya anyways? It's just her mind that allows her to enter Kadath. Well, no not really. You see, Personas are from one's ego and mind, and seeing as how Maki can enter Kadath just by willing it, then this means her will is much stronger than Tatsuya's. And the stronger the will, the stronger the Persona. Here's the line in the translation:
"Nevertheless, how can Tatsuya gain the same power as the Persona users who travelled to the world of the collective unconscious? He already has great talent as a Persona user. If one has enough practise, then through their dreams they'll be able to open the door to the depths of their heart;
Sonomura Maki was one of these people."
Maki is the only one in P1-P2 who can do this. And the interesting thing about the Kadath Mandala? It is home to demons and Shadows
far more dangerous and powerful than anywhere else. In fact, according to the pastebin translation, "Persona users of old who understood the power of their dreams and could visit the world of the collective unconscious also called it the domain of visions". This is actually the reason why Randolph was mind and soul ripped by Nyarly. "Chandraputra reveals to the party that he is in fact Randolph Carter, who had his emotions stolen by Nyarlathotep in the past because of the work Randolph did in mankind's collective unconsciousness and the Kadath Mandala. Through sheer force of will he has been able to take human form and with the return of his emotions he can become a complete human again." This was taken from the
wikia page.
Another reason why the Kadath is so dangerous: Igor warns the Tatsuya that the mental energy of humans is now flowing in the form of shadows and Philemon's power is severely weakened. This was caused by Nyarly himself, to make sure his equal Philemon won't butt in.
So now, we know that the Collective Unconsciousness exists, but no one has ever entered the highest realm where everything is stronger and more dangerous. In fact, the Persona 2 EP team fights gods like
Izanami, Angra Mainyu, and eventually The Faceless God in Kadath.
We also know that Philemon, as the creator of Personas, can grant and take away Persona abilities; he did this with Yukino from Persona 1. He is also equal to Nyarlathotep, who can defeat the ancient, more powerful Persona users like Randolph. Therefore, Philemon and Nyar should be stronger than all Persona users. When you defeat Nyarly in the Tatsuya Scenario, he doesn't really die after all. So we can assume that even though Tatsuya fought against those two, he doesn't fully scale to Nyarly and Philemon.
So! With that in mind, we can set a scaling chain for P1 and P2.
Nyarlathotep = Philemon > Maki Sonomura = Ancient Persona users > Gods and Demons inside Kadath > P2 EP team >> Other Persona users (P1, IS, etc.) >>>>>>>>>>>>>>>>>>>>> Baseline 2-B
And that's it. To my fellow P1 and P2 experts, I'd like to confirm with you all if there's any errors here.
Links to translations here.
