In fanfiction, Natsu could potentially use a new, untested form of his fire magic. Maybe he discovers a way to combine his regular fire with some sort of special element he's been exposed to recently. He could also use his connection with his dragon heritage in a different way. For example, instead of just using his fire attacks, he could use the dragon's sense of smell to detect Gildarts' movements more accurately and anticipate his attacks. Additionally, Natsu could try to get inside Gildarts' head by taunting him, using his brash personality to make Gildarts make a mistake in his attacks or defenses.
Natsu could try his all - out offensive with his most powerful fire attacks. He might start with his Fire Dragon's Roar and then quickly follow up with a combination of punches and kicks enhanced with his fire magic. Another strategy could be to use his environment. If they're in a place with flammable materials, he can set them on fire to create distractions or additional sources of power for his attacks.
Irene could start by creating a shield of magic around herself to protect from Goku's initial attacks. Then, she could use her dragon slayer magic to send out powerful waves of magic towards Goku. She might also try to analyze Goku's fighting style during the battle and look for weaknesses. If she can figure out that Goku has a blind spot in his defense when he's powering up a big attack, for example, she could use that moment to strike. Additionally, she could try to use her magic to drain Goku's energy little by little, slowly weakening him throughout the fight.
One reason could be a new magic source. Natsu might discover a powerful magic that surpasses Gildarts' abilities.
Naruto could also team up with some of his friends secretly. For example, Shikamaru could create a diversion using his shadow - possession jutsu while Naruto sneaks up on Gaara. Or Choji could use his expansion jutsu to block Gaara's sand attacks for a moment, giving Naruto an opening. And Naruto might use his own chakra to disrupt Gaara's control over the sand. He could send out waves of positive chakra that interfere with the negative chakra that powers Gaara's sand defenses.
It depends on how the author of the fanfiction has developed the plot and the characters. They could have given Natsu some special power - up or a unique situation that makes him stronger than Gildarts. For example, the author might have introduced a new form for Natsu that gives him an edge in combat, or perhaps they've weakened Gildarts in some way for the sake of the story. However, in the original series, Gildarts is extremely powerful, so this is a significant departure in the fanfiction.
Well, one possibility is that Gildarts could share some of his powerful magic techniques with Natsu. Since Gildarts is a very experienced wizard, he might see the potential in Natsu and offer some tips on how to better control his fire magic, which is similar to Igneel's. Maybe he could also tell Natsu some stories about his own adventures that would inspire Natsu to become even stronger.
One possible strategy is Naruto using his shadow clones. He could send a horde of clones at Yami to overwhelm him and find an opening. Another strategy could be using his chakra control to sense Yami's movements, especially if Yami has some sort of stealth ability.
In the fanfiction, Gildarts could meet Natsu and Igneel during a time of crisis. Maybe their town is under attack. Gildarts would immediately jump into action, and Natsu would follow suit, with Igneel guiding Natsu from the side. Gildarts might be impressed by the way Natsu and Igneel work together, as if they share a single mind. They could communicate without words, and Gildarts would try to learn from their unique bond. After the battle, Gildarts would offer to train Natsu further, seeing his great potential enhanced by his connection with Igneel.
Latios might start by using a protective psychic shield. This would prevent Metagross's initial attacks from doing damage. Then, it could use its flight to gain altitude and survey the battlefield. When it spots an opening, it can dive down and launch a combination of Dragon - type and Psychic - type moves. For example, it could first use a weak Psychic blast to stun Metagross slightly and then follow up with a full - force Dragon Pulse. Since Metagross is a Steel/Psychic type, the Dragon - type move would be super - effective against it, especially if Latios can land a direct hit.
Well, it could involve Naruto finding out about his long - lost brother Gildarts. Maybe they meet in a strange new world that is a mix of the Naruto and Fairy Tail universes. They then team up to fight a common enemy using their combined powers.
A plot could be that Natsu and Lisanna have been longing for a baby. They go through a magical ritual in their guild to increase their chances of having a child. Once Lisanna becomes pregnant, the whole guild gets involved. Everyone is excited and offers their help. Natsu becomes super protective of Lisanna and the unborn baby. There could be a sub - plot where an enemy tries to target Lisanna because of the powerful baby she is carrying, and Natsu has to fight to keep them safe.