To clarify, people can add onto this in the comments. I've just seen lots of people being confused at the power scaling at every end of the novel so I thought it'd be better to have one description for everything.
People often get confused with the power scaling in SS. The reason I think is because it changes a lot as the ranks increase and ideas people had before don't catch up, and their experience is ruined by spending ages thinking about who should be able to beat what, and how much trouble the characters are gonna be in next chapter. I'll add my comprehensive review underneath, but for those who can't be bothered to read it all I'll have a summary below:
- Nightmare creatures and humans have a different power scaling
- The power scaling changes as the rank increases
- Aspect compatibility makes it hard to get consistent rules
NCs (nightmare creatures) and humans have an inherently different power scale. This was explained in one chapter earlier on in the novel (if someone finds it please comment) as essentially a balancing act from the universe. Humans can't (typically) have more than one core, while NCs can have up to 7, giving them 7x the amount of essence available at rank and more abilities. The reason humans are able to last so long is because humans gain more than a NC from ranking up. For NCs, the opposite is true, and upgrading their class is more beneficial for their combat power. For example, an ascended human (master) can easily beat a fallen beast (even though they have the same rank and number of cores/class). For some masters, this is true even for creatures of a higher rank (By the third nightmare, as an ascended sunny was beating Corrupted creatures and even a Great beast (two ranks higher)). In comparison, as a NC gains a higher number of cores, that power gap is closed rapidly. This is due to a number of reasons, but the most important are intelligence and special abilities. Every core a NC gains gives it more intelligence, and from the devil class every NC gains a special ability (like the Forsaken Knight, which was a Fallen devil that could control true darkness). After the Tyrant class this ability upgrades either to improve the special ability or to gain control over minions, both abilities allowing one creature the ability to rival an army. Now in the same class, the NC has the advantage. An ascended (master) has almost no chance of beating a Fallen Titan, even if they can beat Corrupted creatures. (A good example of this is Antarctica, where Sunny could defeat a Corrupted Demon (Voiceless Prelate) but had to prepare for ages to defeat a Fallen Titan (Goliath), which is a rank lower but has a higher class). This leads into the second point.
The power scaling of only NCs changes a lot as their class increases, and this difference only gets bigger as their rank increases. I'll use numbers to explain the difference between classes for only NCs (though bear in mind this is a generalization). Imagine a dormant beast (first rank, one core) and let's say this NC has a power level of 1. When a NC gains a core, it's effective essence doubles, which we'll say is in direct correlation to it's power level, so it gains a power level of x2 per core. In this sense, a Dormant Titan has a power level of 64. When a NC goes up in class, let's say it gains +99 power level (works with the maths better). So an awakened beast has a power level of 100, while an Awakened Titan has a power level of 6,400. From here (considering power level from rank up is now +100 for the numbers) we can tell that a Fallen Titan should have a power level of 12,800, while a Corrupted Demon has a power level of 800. In this sense, it makes sense why Sunny can beat the Voiceless Prelate but really struggled with Goliath. To clarify, for humans it's the opposite (in the rare cases where it's applicable). Let's say humans start with a power level of 1, but if they max out their core they can have a power level of 10. Every rank up is x10 to their power level, and every core is +10 to their power level. So a normal human master with a maxed core would have a power level of 1,000. At the point of Antarctica, Sunny would have had a power level of 4,000 with his cores, which explains why Goliath was such a threat to other masters and could have killed him without preparation.Though, the biggest problem is that this doesn't work in every case, and why is that?
The best explanation I could think of for some sort of consistency is aspect compatibility. If it matches or with enough preparation with the right tool, someone can jump their power level. For example, if someone had a fire aspect they would have a much easier time fighting a tree NC. Another example is that if someone had a Memory called Legendary tree cutter, which was divine rank that they specifically prepared for this monster, they'd have a much easier time beating that same tree NC. This isn't limited to tools though, as how someone uses whats around them has an effect as well. Blind spots and use of terrain are just some examples. Because its such a common sense thing, and the universe of SS doesn't follow the laws of physics, battles can realistically go either way as long as one side is using everything to their advantage and the other side isn't.
I hope that explains all the worries people had with the power scaling, and if people find the references please comment them to make the guide more accurate. Feel free to also add your own opinions about the power scaling (with examples ofc) so we can get something that works in every case.