Who could be the main antagonists in a 'natsu marries cana fanfiction'?

One possible plot could be that Natsu realizes his deep feelings for Cana over time. They might go on an adventure together where Natsu protects Cana from a powerful enemy. This shared experience makes them closer and Natsu decides to propose. Their wedding could be a grand affair with all their friends from the guild celebrating.

A group of dark fairies could be the main antagonists. They might be jealous of Natsu's power or his unique status as a fairy and try to undermine him at every turn.

The Malfoy family could be antagonists. They might see Harry as an enemy still and not want Daphne, a pure - blood, to marry a half - blood like Harry. They could try to create problems between the two, spreading rumors or trying to sabotage their relationship.

It could be another guild that sees Natsu as a threat. They might find out about Lucy kidnapping Natsu and try to use the situation to their advantage. For example, they could try to steal Natsu's magic or get information out of him while he's in a vulnerable state. Another possible antagonist could be a character who has a grudge against Lucy. They might try to stop her from getting away with the kidnapping or use it as a way to get revenge on her.

There could be a powerful demon from another dimension. As Natsu becomes an adult, his magic signature becomes stronger, which attracts this demon. The demon wants to possess Natsu's power for itself and will stop at nothing to achieve this goal. It would be a formidable foe, with abilities that Natsu has never faced before.

Perhaps there are other divine beings who are jealous of the cat goddess's relationship with Naruto. They could see Naruto as an unworthy mortal and try to disrupt their marriage. These divine antagonists could use their powers to create all sorts of troubles for Naruto and the cat goddess, like causing natural disasters or sending powerful minions to attack them.

In this fanfiction, the antagonists might be a group from Koneko's world who oppose her relationship with an outsider like Naruto. They might fear that Naruto will bring chaos or change their traditional ways. They could try to separate them by any means necessary, including using their own unique powers against Naruto. Also, some of the rogue ninja from Naruto's world who are jealous of Naruto's new relationship could also cause trouble.

A powerful dark guild could be the main antagonists. They might be jealous of the combined power of Natsu and Mirajane's family and seek to destroy them to gain more power in the magical world.

Maybe a rival guild that is jealous of Fairy Tail's new addition. They might think that having a baby with such strong magical potential in Fairy Tail gives them an unfair advantage. So they try to kidnap the baby to either keep it for themselves or use it to bargain with Fairy Tail.

Well, one possible plot could be that they are on a dangerous mission together. In the heat of the moment, as they face a powerful enemy, they realize their deep feelings for each other and share a kiss. It could be a moment of both passion and a new beginning in their relationship.