Honestly, the drastic change in the fight (when Acnologia was knocked out of the sky), Face was activated, I don't find it a coincidence that the moment Acnologia gets knocked out of the sky was the moment Face was activated, it definitely affected him, plus, the moment Face was destroyed by the Parent Dragons Acno got right back up and immediately overpowered Igneel. I think Face fucked with Acno and helped out Igneel. That was the most damage we've seen Igneel give him before taking his arm. I'm doubtful Acno would have been knocked out without Face. Most of the fight was also off panel, the parts we see is Acno no-selling Igneel's initial roar (when Igneel grabbed Natsu and said that his roar didn't do anything to Acno) and Acno getting his arm bitten off along with him being knocked out of the air. Him getting his arm bitten off can be pointed to him being reckless.
But, I think it would be the same diff (in Igneel's favor this time) due to Acnologia being more cautious and careful. Igneel seems to be on his level, but Acnologia had no problem physically engaging. I think a one-armed Acnologia would be more careful and keep his distance which would give Igneel more trouble as Acno is completely immune to his flames and WILL eat them this time around to amp himself up and replenish himself meanwhile, Igneel can get extremely hurt if hit with full powered magical attacks from Acno.
However, if we take Zeref's statement of Acno never being challenged (despite it being after his fight with Igneel), it could be assumed Acno was fucking around with Igneel. I'm not saying he was, I'm saying it could be argued as Zeref himself watched the fight and still mentioned that he wasn't ever challenged (also implying that Igneel didn't challenge him 400+ years ago either), but, by shown feats, Acno>=Igneel, by reliable statements in Zeref (who was watching) Acnologia>Igneel.
Yeah, I was wondering if Face did something there as well. It seemed like too much of a coincidence. In fact, that was my initial reaction, I was like yeah Face fucked Acno there.
But, shouldn't Face also technically nerf Igneel the same way as well? I'm not sure if Face can be attributed to what Igneel did.
Fair point about Acno maintaining his distance if a hypothetical one armed Acno fought Igneel.
Logically, yeah. In fact, without CIS, this should be Acno's best bet against a dragon who is relative to him in physical stats, to minimize damage. Just keep the distance, and spam spells. He can also eat earth, air etc, if it ever reaches a point where he is running out of gas.
I think Acno engaging more in physical combat is just his in character demeanor. It's because he wants to kill dragons with his own hand, rather than relying on spells. So, in character Acno probably won't rely on keeping distance in a hypothetical battle, even if he only has one arm, which might cost him the battle. But a no CIS Acno definitely will.
Basically. If there is no CIS: Acno should take it high-extreme diff against Igneel, Ignia etc, even if he only has one arm. Would be mid-high diff if he has both arms.
But in character Acno: wins high-extreme diff against Igneel/Ignia with both arms. Probably loses extreme diff with one arm
I honestly wouldn't consider Zeref's statement at face value.
I don't think Acno or anyone can claim with a straight face that he didn't take a fight seriously, where he got knocked on his ass and lost his arm.
Simple, Ignia doesn't have any feats backing up his hype and statements. He had a chance to go after Acno, but didn't take it, instead he waited until he was dead before talking shit about being able to kill him, Ignia strikes me as someone who is very arrogant but is all bark when it comes to people tougher than him. even with Selene he needed a cheap shot to beat her rather than defeating her in fair combat. I just don't think he's on the same level as Acnologia and his dad.
Didn't Ignia also say that he was gonna fight Acno, but then he "died" in Alverass arc?
Ignia = Igneel is what makes narratively most sense to me. I think this is Mashima's intent with Ignia.