I know many of you will not agree with this list, but this is the best I can create. I'm just being honest here. This list is not only based on pure destructive power and the number of characters, but also considers the context within the respective universes. DxD characters are generally considered stronger in this regard.
However, I also considered their feats and what is stated about them across multiple fan pages, as well as my own understanding of each character's abilities. This list can change based on feedback from you all, or once my Patreon is created, where you'll have the power to influence things in future chapters.
I repeat again: I've given reasons for why they are placed where they are. Additionally, Itachi, Issei, and Vali are not included for obvious reasons, as their powers will change drastically in the future.
Lastly, if you are disappointed by this list, you should read until Chapter 30 to understand that I have not intentionally made any anime characters weak or strong. This list is solely to give you an idea of power levels and rankings so you can understand how these characters compare to each other.
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List (not includes boruto characters)
0. Kaguya Otsutsuki (Naruto)
Strongest Feat: Created and controlled multiple dimensions with their own solar bodies, and wielded the Truth-Seeking Orb, capable of annihilating worlds. Kaguya is the only character on this list considered too powerful for any single entity to defeat. She was only sealed away through the combined efforts of Naruto, Sasuke, and the power of the Sage of Six Paths. She is weaker than great red and ophis in terms of power that's why I put her in 0 rank.
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1. Great Red (DxD)
Strongest Feat: Dominates the Dimensional Gap, can clash with Ophis on equal terms, and has the power to destroy multiple worlds.
Reason: Great Red is considered the strongest, followed by Ophis, according to the DxD author and the fanbase. However, he was also effortlessly killed by Regalzeva, the Fierce God of Evie Etoulde.
Fan Source: "This doesn't mean that Great Red wasn't unaffected by everything, as a being such as the Dragon Eater could affect him; he, in fact, was effortlessly killed by Regalzeva."
On the other hand, Ophis was weakened to the point that Shiva stated he didn't have any interest in killing her in her weakened state.
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2. Ophis (DxD)
Strongest Feat: Possesses infinite power and can erase gods or entities from existence at full strength. The only reason she is ranked third is because she lost much of her power, leaving her vulnerable and susceptible to being killed.
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3. Shiva (DxD) (Not in Fanfiction)
Strongest Feat: Holds the power of destruction stronger than Sirzechs and can rival or surpass beings like Trihexa. Shiva was kept as a last line of defense to stop Trihexa if all other efforts failed. He even stated that he could stop Trihexa and seal it, though he couldn't kill it and the world will be destroyed.
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4. Trihexa (DxD)
Strongest Feat: Required a coalition of god-class beings to seal it. The reason he is ranked fourth is because he was once sealed. Trihexa is a mindless entity, but its sheer destructive potential places it high on the list in terms of power.
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5. Hagoromo Otsutsuki (Naruto)
Strongest Feat: Created the moon, split the Ten-Tails, and granted the power of Six Paths to Naruto and Sasuke.
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6. Naruto Uzumaki (Six Paths Sage Mode, Baryon Mode) (Naruto)
Strongest Feat: Defeated Isshiki Otsutsuki and punched Kaguya in Six Paths Sage Mode.
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7. Sirzechs Lucifer (DxD)
Strongest Feat: Annihilated space-time and all surrounding matter with the Power of Destruction.
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8. Indra (DxD) (Not in Fanfiction)
Strongest Feat: Defeated the Dragon King Vritra alone.
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9. Sasuke Uchiha (Rinnegan + Both Hands) (Naruto)
Strongest Feat: Sealed Kaguya and battled Isshiki Otsutsuki.
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10. All DxD Characters Considered in the Top Ten