u/Muted_Personality107

I find this question interesting because, aside from the early volumes, Issei rarely fights in his base form, even during training or sparring.

The only instance I could think of would be Volume 14 during the Magician ambush but he didn't really win and they ended up getting away.

Since then, he's only gotten stronger, reaching High-Class level as of Shin 1 as confirmed by Ddraig and the Artificial Devils.

That being said, who do you think is the strongest person he could beat in base level?

By base I mean no Boosted Gear or Boosted Gear-related abilities as it wouldn't be something he can do naturally on his own.

Things like Fire Breath (he should be capable of that), the Ascalon swords, and Dragonization are allowed as they dont necessarily increase his power, at least Dragonization doesn't seem to be based on how he didn't defeat the magicians.

This is really the outcome that makes sense for their battle in Shin 5 (assuming that ever comes)

And to anyone who says "Oh but Issei is weak to technique types"

The power gap is simply too massive for that weakness to make a difference, especially given Issei's recent battle against Kiba, who lost pretty quickly.

He only struggled against someone like Cao Cao or Vidar due to being strong AND for having better technique, where as Kiba solely had the latter.

Who knows, Maybe Diehauser will have gotten strong by then too, but it won't be likely enough to make an impact.

Hypothetically, say that Katerea was revived by the Alliance of Hell via unknown means, likely thanks to the influence of Hades.

He forcibly recruits her into their forces and during the Hell Disaster, she encounters Rias (without Gasper at her side) and Fallen Angel Akeno.

She has been permanently enhanced to Satan-Class without the use of Ophis’s snake and fights them herself.

Neither side will receive further aid.

Who takes it and at what diff?

Hypothetically, say that these two encountered each other during the war against the Qlippoth Faction and fought to the death.

I always found this match-up to be incredibly interesting because it's essentially between two people who are sitting on different extremes of good and evil; Vasco known for his benevolence and wisdom despite his God-like power, and Rizevim, known for his absurd cruelty and….somewhat significant power despite only having one fight in the whole series 😂

The battle is set in an artificial space with a country-sized landmass (I.e United States) and will not receive help or healing (example: Phenex Tears)

I will separate it into two rounds

Round 1: 87-year-old Vasco with the Durandal Replica from Vol 19

Round 2: 50-year-old Vasco from Vol 24 and Shin 2 with Durandal II

Hypothetically, let's say Sirzechs manages to leave the Isolation Barrier Field for some time off, resting, spending time with his family, etc.

He hears of Issei’s accomplishments, both in the tournament and in Team DxD, and is thoroughly impressed by his growth.

He harkens back to when they first fought in Vol 8 and how one-sided it was, wanting to test Issei again, especially after hearing how he now rivals Satans in his crimson armor.

The fight takes place in an artificial dimension created by Ajuka that's roughly the size of say, the United States.

Both are unable to power up further as both need to remain in good condition in case a crisis occurs or for when Sirzechs has to go back to the Isolation Barrier Field.

All other abilities are welcome and the fight ends when either combatant is incapacitated or concedes.

Who takes it?