This chapter will explain how the power scaling will work in this fic since DxD's is really wonky. I'll explain the scale, how different races get stronger and the top 10 I'll be working with. I don't care if it's not canon, it's the one I'm using, period.
-----(Scaling)-----
Low-Class:
Beginner: Can destroy a strong tree
Intermediate: Can destroy a small boulder
Peak: Can destroy steel (a car)
Mid-Class:
Beginner: Can destroy a small house
Intermediate: Can destroy a gym (Yubelluna in the rating game)
Peak: Can destroy a small building (3 stories or so)
High-Class:
Beginner: Can destroy a school (Kuoh Academy)
Mid: Can destroy a village
Peak: Can destroy a small town
Ultimate-Class:
Beginner: Can destroy a city (Tokyo)
Mid: Can destroy a Prefecture
Peak: Can destroy a small country (Lebanon)
Satan-Class:
Beginner: Can destroy a country (Japan)
Mid: Can destroy a big country (Australia)
Peak: Can destroy a small continent (All of South America/Europe)
Super-Class:
Beginner: Can destroy the moon
Mid: Can destroy Asia
Peak: Can destroy the Earth
Dragon-God:
Not Measurable (OP)
-----()-----
Now I'll try and give examples so it's clearer:
Two Wings = Low-Class (Raynare)
Four Wings = Mid-Class = Low-Class Dragons (Yubelluna)
Six Wings = High-Class = Mid-Class Dragons = Lesser Gods (Rossweisse)
Eight Wings = Ultimate Class = High-Class Dragons = Mid Tier Gods (Cao Cao, Yasaka with no leylines, Vasco Strada)
Ten Wings = Beginner Satan Class = Ultimate Class Dragons = High Tier Gods (Olympians, Kokabiel,)
Twelve Wings = Peak Satan Class = Dragon Kings = God Kings (Odin, Zeus, Amaterasu)
-----(Strengthening Methods)-----
This section is an explanation on how different races get stronger so here we go:
Devils: Age and Contracts, the older the devil is and the more contracts they have, the stronger they are. Training helps but they don't need it. Without training, devils cap out at Peak High Class.
Angels: Good Deeds and Blessings(former), the more good deeds an angel does, the stronger they become thanks to Heaven's system tracking their activities. They are rewarded for good deeds and were capable of getting instant strength boosts in the past thanks to God but his death has prevented that action. Normal Angels are restricted to Peak Ultimate Class since they cannot evolve to seraphs without God's approval. Training helps of course.
Fallen: Training. Their banishment from Heaven has hurt them badly and so, they can only get stronger by training. It's why they rely on sacred gear wielders,
Yokai: Exposure to negative emotion and age. Yokai can get stronger by inflicting negative emotions onto humans and absorbing said emotions. Some special Yokai such as kitsune can also get stronger with age. They are capped at Peak Ultimate Class with no training. Sun Wukong is the only known Yokai to have broken the cap.
Gods: Belief and Followers. A God gets stronger the more believers they have. Their Peak of strength is dictated by their domains. Shiva is so strong because his domain of destruction is primal and extremely strong. Training cannot increase a God's strength but can allow them to create new techniques to become capable of defeating those stronger.
Humans: Pure training and effort. Sacred Gears help, but no pain no gain.
-----(Ranking)-----
Now the Top 10 Raking and their strength:
10-Fenrir (Peak Satan Class): Exception among exceptions and is chosen because of his anti divine properties.
9-Hades (Beginner Super Class): Exception as well, gets his strength from his connection to the underworld and his control of the majority of it.
8-Ajuka Beelzebub (Beginner Super Class): Strong but his lack of firepower compared to Sirzechs put him in this spot.
7-Thor (Intermediate Super Class): The strongest God outside the Hindu pantheon.
6-Sirzechs Lucifer (Intermediate Super Class): The strongest creature outside the Hindu pantheon.
5-Indra (Peak Super Class): Leader of the Hindu, still can't beat Shiva
4-Shiva (Peak Super Class): It's Shiva, enough said.
3-Ophis (Dragon God): The weakest Dragon God.
2-Trihexa (Dragon God): The biggest threat to the entire world
1-Great Red (Dragon God): The strongest being in existence and guardian of the dimensional gap.
-----(Clarification)-----
I decided to add this section to explain some things. If a Mid-Class is fighting a High-Class, it doesn't mean that the Mid-Class will automatically lose. The power scaling only measure destructive powers and doesn't take into consideration things like techniques or weapons. a Mid-Class exorcist could defeat a High-Class devil using skill and holy items. It's how Strada defeated Kokabiel, at least in my AU. He did it using holy weapons such as Durandal and technique plus having Kokabiel underestimate him because he is human. Basically, while your position on the power scale is important, it's no the end all be all.
That's everything, hope this helps in understanding my scaling better.