In the Fairy Tail universe, Igneel is extremely powerful with his fire - based magic. However, Acnologia is known as the most powerful dragon. I think Acnologia would win. His power is on a different level and he has shown to be nearly invincible in most battles.
One epic moment could be when Igneel unleashes his most powerful fire attack, a huge blaze that engulfs the area, and Acnologia just withstands it with his dark aura. Another could be when Acnologia lunges at Igneel with his massive jaws, and Igneel dodges at the last second.
In many Fairy Tail fanfictions, the battle between Natsu and Acnologia is often depicted as extremely epic. Natsu's fiery determination and his unique dragon - slayer magic make for an interesting contrast against Acnologia's overwhelming power. Some fanfictions might have Natsu discover new forms or powers in order to stand a chance against the fearsome Acnologia.
I'm not sure if there is a specific fanfiction with the exact title 'naruto is igneel fairy tail fanfiction'. Fanfictions can be quite diverse. It might be a very creative crossover where the author imagines Naruto in the world of Fairy Tail with a connection to Igneel. Maybe Naruto has some of Igneel's powers or characteristics in this fictional scenario.
Well, in this fanfiction, Igneel's return could bring a huge shift in power dynamics. His relationship with Natsu might be explored more deeply, like they could have some intense training sessions. Also, it might lead to new quests for the Fairy Tail guild as Igneel's knowledge could be used to combat stronger enemies.
Some writers characterize Acnologia as a misunderstood loner. They show that his actions of destruction are a result of his past traumas. Others might make him more of a power - hungry villain who just wants to rule over all. There are also those who give him a sense of humor, which is a very different take from his usual brooding and menacing self in the original series.
One significance could be the emotional boost for Natsu. After so long without Igneel, having him back would be a huge source of comfort and strength. Natsu could become even more determined in battles.
A common theme in such fanfictions is Natsu's unwavering courage when facing Acnologia. He might not be as strong as Acnologia at first, but his will to protect his friends and the Fairy Tail guild drives him forward. His dragon - slayer magic could potentially have some hidden aspects that are only revealed during this encounter.
The guild as a whole would likely mobilize. Erza would start formulating a strategic plan. She'd consider the strengths and weaknesses of Acnologia and figure out the best way to approach the situation. Gray would also be ready to fight, using his ice - make magic to support the rescue mission. They would all be united in their determination to get Lucy back safely.