Who could be the main antagonist in the 'natsu becomes op fairy tail fanfiction'?

In the fanfiction, perhaps Natsu has a fateful encounter with a powerful magical being. This being could transfer some of its essence or powers to Natsu. For example, it might be a dragon from a different dimension that gives Natsu the ability to not only control fire on a much larger scale but also to manipulate other elements to some extent, thus making him OP. He could then use these newfound powers to take on the toughest enemies in Fairy Tail, like the dark guilds and their powerful leaders.

It could be Zeref. Since he has a complex relationship with Natsu in the original story, he might manipulate things behind the scenes to make the Fairy Tail guild betray Natsu. Maybe he wants to isolate Natsu for his own evil plans.

Perhaps an old enemy of Fairy Tail who sees Natsu as a new threat. They might target Natsu specifically to prevent him from strengthening the guild. This antagonist could have a long - standing grudge against Fairy Tail and see Natsu as the new hope for the guild, so they try to eliminate him before he can fully join.

It could be a powerful wizard who has a grudge against Fairy Tail and sees Natsu as a new threat. This wizard might have been secretly observing Fairy Tail for a long time and when Natsu joins, they decide to strike. Their magic could be something unique like shadow manipulation or time - based spells.

It could be a dark wizard who has a grudge against Fairy Tail. This wizard might be the one who made Natsu lost in the first place, by using some devious magic to separate him from his guild.

It could be a rival wizard from another guild. This wizard might be jealous of Natsu's power and popularity within Fairy Tail. So, they fabricate evidence to get Natsu expelled, aiming to not only remove him as a competitor but also to create chaos within Fairy Tail. They could continue to be a thorn in Natsu's side as he tries to clear his name and get back to the guild.

It could be a powerful dark wizard who has a grudge against Fairy Tail. This wizard might see Natsu and Mirajane's joining as an opportunity to strike at the guild when it's in a state of flux. He could be someone who was once defeated by Fairy Tail in the past and has spent years building up his power for revenge.

It could be a rogue dragon slayer. Someone who has turned against the ways of dragon slayers and wants to destroy Fairy Tail for some personal vendetta against Natsu or the guild as a whole.

A powerful dark wizard who has a vendetta against Natsu. Maybe he blames Natsu for something that happened in the past, like the destruction of his dark guild by Fairy Tail. So, when Natsu and Happy leave Fairy Tail, he sees it as an opportunity to get revenge.

Another option could be a dark wizard from the past who was once defeated by the founders of Fairy Tail. But Natsu's time - traveling causes some sort of ripple effect that brings this wizard back to power. He then wants to take revenge on the guild and sees Natsu as a symbol of the future that he wants to destroy.