If E.N.D is the strongest Demon in the Books of Zeref and if Acnologia can slay countless dragons, is it possible for E.N.D to slay Acnologia?
I mean, when you think about it, Natsu's dad couldn't slay E.N.D, so is it possible for the Demon to slay a dragon like Acnologia?
I highly doubt it.
First of all, we have no evidence to suggest that any slayer magic is of a higher tier than any other slayer magic. Wendy and Chelia were about equal when they fought, and Natsu actually defeated Zancrow in combat despite Zancrow's God Slayer magic. Therefore END's Demon Slayer magic isn't necessarily better than Natsu's Dragon Slayer magic.
Secondly, Natsu is END. That means that we don't have any evidence to suggest that END is anything more than Natsu wielding Fire Demon Slayer magic as effectively as he wields Fire Dragon Slayer magic.
So looking at the matchup, I would argue that Natsu is actually better suited to 1v1ing Acnologia as a Fire Dragon Slayer than as a Demon Dragon Slayer. You see, slayer magic is designed to defeat the entity they are named after. That means Fire Dragon Slayer magic is more effective against dragons than Fire Demon Slayer magic. (Chapter 301, Zealconis states that humans were given the magic to slay dragons. That's logically Dragon Slayer magic, and you can deduce that X Slayer magic means magic to slay X).
The reason Zeref designed END is because he wanted to get hit with the most powerful Demon Slayer Magic that existed, since Demon Slayer magic is more effective against his demon body.
At any rate, if Natsu with his super-effective-against-dragons magic can't beat Acnologia without the power of friendship, I doubt he could do so with less effecive magic.
Bryan Tan answer has described most of the part. I am going to add some part where they actually fight.
Natsu Dragneel is E.N.D, Etherious Natsu Dragneel, brother of Zeref Dragneel, died 400 years ago and resurrected as Etherious demon but not from the Book of Zeref.
If E.N.D is the strongest demon in the Books of Zeref and if Acnologia can slay countless dragons, is it possible for E.N.D to slay Acnologia?
No, E.N.D(Natsu) can't win Acnologia if they fight one on one. Natsu uses Dragon slayer magic. Acnologia was a dragon slayer too, who turned into a dragon because he overused his dragon slayer magic.
In Chapter 540-44, when all the dragon slayer are trapped in Ravines of time, they all together fight with Acnologia. If we see the fights between all the dragon slayer and Acnologia, he is overwhelmingly powerful.
His dragon body was sealed by Lucy in Fairy sphere with the help of combine power of whole continent which made his body in Ravines of time freeze. Taking this as a chance Natsu defeats Acnologia with the help of the power received from all the dragon slayer.
so is it possible for the Demon to slay a dragon like Acnologia?
No, magic has no effect against him. So slaying Acnologia is impossible.
Somebody might be thinking that if magic can't kill then how Dragon Slayer magic can? Read Dragon Slayer Magic thoroughly for better grasp
E.N.D can defeat Acnologia in some possible ways.
Natsu Dragneel in episode 276 and 277 is way stronger than 1 year ago, that's just 1 year, he took out the new strongest guild in Fiore in 1 shot, so maybe if he can use his dragon slayer magic in his fullest potential, he can kill Acnologia.
Some people say that he can't defeat him because Acnologia turned into a dragon by overusing dragon slayer magic, but I believe it's wrong. Natsu and all other dragon slayers could turn into dragons as well if their parents didn't seal them inside their bodies to protect them from physically transforming into a dragon.
I believe that E.N.D cannot defeat Acnologia.
He was reborn from Etherious matter like the other demons but given a different purpose. He wasnt given a curse power. Igneel could defeat E.N.D but didn't because Igneel loved natsu. Later on Zeref gave Natsu to Igneel so he can raise him and teach him magick. Fire dragon slaying magick.
Acnolgia slayed Countless dragons and gained a reputation and called himself the King of Dragons.. He Mastered the Art of Dragon Slaying magick. His power rose from the Tenrou sland ard to Alvares arc. As Erza said. He's on a different level since Tenrou island. He had the power to rule the world if he wanted.
Zeref wanted Fairy heart to defeat Acnolgia. Even though they had the Sprigann 12 and Military power.
If E.N.D is the strongest demon in the Books of Zeref and if Acnologia can slay countless dragons, is it possible for E.N.D to slay Acnologia?
I mean, when you think about it, Nastu's dad couldn't slay E.N.D, so is it possible for the Demon to slay a dragon like Acnologia?
Yes. I believe it’s possible for E.N.D could beat Acnologia. Though, not a lot of information has been stated about END but he’s happened to break through a time freeze. Assuming he’s using curse power since most demons do, it would be easier on Acnologia. Also, the reason gray was able to go toe-to-toe with natsu was because he had demon slayer magic. A magic that was made to deal with those type of demons and curses. It’s been shown when gray mange to freeze curse power and he was immune to the ‘thorn curse that removes your existence.” Also, the reason Igneel didn’t kill natsu wasn’t because he wasn’t strong enough. It was because he wanted to raise him. If you wanna add ‘dragon cry’ which some people say isn’t canon even though it’s mentioned in the manga, he uses E.N.D form to slay a dragon. So yes, I believe it’s possible for E.N.D to slay Acnologia. Also, a lot of people keep saying that Acnologia over used Dragon slayer Magic which caused him to turn into one but that isn’t true. That was a side effect of dragon slayer Magic which was shown with Erza’s Mother. Igneel and the other dragons created the anti-bodies which stop natsu the rest of the slayer from transforming. The reason Acnologia is OP is because he slay hundreds of dragon and bathed in their blood. It’s been stated that dragon slayers power could increase by bathing in dragon Blood. It’s been said by rogue and stings dragons. Though it’s not been said why or how he’s able to eat magic and is immune, but my theory is that he’s so op that he’s now able to eat any element also because he absorbs dragon souls too. The only reason why natsu and the slayer beat Acnologia was because they used Fairy spheres while he was on a boat. A dragon slayers weakness. Anyways, E.N.D was supposed to be strong than Zeref and I’m sure they’re gonna release more of him in the 100 year quest. But in my opinion, yes, E.N.D could beat Acnologia. He was able to break through frozen time, slay a dragon (dragon cry) and even burn almost everything in his path. Plus, it’s stated that demons have another form so we probably haven’t seen full E.N.D
I believe that Natsu, in the most powerful END state that we have seen, could beat Acnologia, this being when he at Ignia’s flames in the 100 Year Quest manga. It is stated by the guild master of Magia Dragon (the employer of the quest) that the Holy Pentadrakes or Five God-Dragons are all as strong if not stronger than Acnologia. Taking this into account by the fact that Natsu was stronger than Merciphobia in his END state, we can conclude that 1 year after the when Natsu actually fought Acnologia, he is strong enough to beat him.
If we are looking at JUST Natsu’s raw power outside of END, I would say that he could not beat Acnologia.
There is a possibility because the main thing with acnologia is the fact that he can consume any sort of magic the reason E. N. D might beat him is because he doesn't use magic he uses curse power and being the strongest in the books of zeref means he was stronger than mard geer who fought celestial spirit king also he in his incomplete demon form was still powerful enough to overpower time stop he was simply stronger than any sort of slayer magic at that point so as hard as it is to do it, once he controls his demon form he can very likely beat acnologia
Natsu in END's form can beat Acnologia as magic doesn't work well against Acnologia but END's curse power can.
When Acnologia entered the battle, then Mard Geer said that Acnologia is afraid of END and have come to slay END before its reborn again. That proves it.
Also, END defeated a god which uses magic and is also the most powerful curse user. Curse is a power greater than magic.
