MC has a meltdown after facing a twisted interpretation of Romeo and Juliet, and after finding out that a literal hell resided in the heart of a city (where people get resurrected/are perpetually living as a fused mass of flesh). Since they came into the world from Earth and knew little about violence + had morals from Earth, they were mostly naive, but gradually understood that violence was the only language that people could understand, dubbing it the Universal Language.
MC becomes a multi-staged boss after this realization, becoming the manifestation of their woes and civilization as a whole, requiring the heads of the biggest reality-altering corporations to contest her, as well as an Angel. She is bested by the power of the weakest character in the story -> who confronts the MCs own beliefs to bring them back, but not after one hell of a beatdown, involving callbacks and entities as far back as hundreds of chapters ago.
It's the greatest so far (imo. There are lots) because the story can be divided into two major parts: Before and after the fight, since it's one of the MCs pivotal character arcs and massively shifts the gears of the story. MC takes command over the reality-altering corporations as 'The Head' who allowed 'Hell' to exist in the first place, and tries to make the world a better place, but also understands that it cannot be done without dabbling in necessary evil, like condemning criminals to a program that generates energy from their suffering - Which ironically created her own version of a 'just' Hell to fuel her paradise.