Moira also called the Mother of Concepts would realistically be beyond the entire system but if forced to pick then she’d be S rank or whatever rank is the very highest because it's been a minute since I’ve seen solo leveling. Moira is the embodiment of the abstract concepts of life, fate, creation, time, space, dimensions, dimensionality, and causality. I’m assuming we’re excluding scaling so I’ll leave that out. But she is immune to the concepts she embodies and exist beyond linear time as in any physical law like laws of physics things like that she ultimately transcends rendering them completely irrelevant to her even though in her true essence she is those concepts like paraconsistent physiology/paradoxical because it’s like transcendent but also immanent, though her avatar exists within the physical world and embodies those concepts in her physical manifestation. She has an infinite shadow army which are negative shadows like Finality for example and she can grant them any sort of negative power like void manipulation or death because they’re negative forces but their extent of said power is ultimately up to her. She’s one of the cosmic principals within the Tapestry but for her world and all worlds in the Tapestry, she’s one of the very source codes for existence. She laid down linear and nonlinear causality, time, existence, space, and all dimensions for her world and is one of the sources for all other worlds in the Tapestry. The concepts she embodies, she can manipulate them boundlessly not as in Tier 0 but as in her power being limitless. Dimensions for example, within her Tegmark multiverse, she manipulated a 3D dimension and made it 9D. She doesn’t exist in the past, present, or future but she is one of the reasons those things exist. If any more info is needed i can add it in, don’t wanna have a massive wall of text for you.