Who could be the main antagonist in 'hiccup and heather married fanfiction'?

It could be a rogue ninja who has a vendetta against Naruto and sees Heather as a way to get to him. Maybe this ninja was once defeated by Naruto and now wants to use Heather as bait or hurt her to break Naruto's spirit.

It could be the school bully. In the context of their relationship, the bully might target Charlie Brown specifically when he's with Heather, trying to embarrass him in front of her. This could create tension in their relationship as Charlie Brown might start to avoid Heather to protect her from the bully's taunts.

It could be a dragon hunter who sees Hiccup in his dragon form and wants to capture him for study or to use his unique abilities for evil purposes.

A rogue dragon rider who has different ideas about how to treat dragons. He might see them as tools for power rather than friends like Hiccup does. This rider could be causing trouble for Hiccup and his tribe by stealing dragons or using them to attack other tribes.

A new dragon - hunter could be the main antagonist. He might be extremely skilled and ruthless, and Hiccup hides his strength to better understand this new threat and find a way to defeat him without putting his village in immediate danger.

Maybe a jealous rival from within the village. This person has always been envious of Hiccup's relationship with Toothless and his status as a dragon trainer. When Hiccup gets struck by lightning, this rival spreads rumors that Hiccup is now cursed and should be ostracized. He tries to turn the villagers against Hiccup in order to take his place as the leading figure when it comes to dragons in the village.

Maybe a rival Viking tribe that has a different view on dragons. They see dragons as a threat rather than friends like Hiccup and Valka do. So they try to disrupt the peace that Hiccup and Valka are trying to build between the Vikings and the dragons. They could be constantly causing trouble, stealing dragon eggs or attacking dragons, which would force Hiccup and Valka to take action against them.

Well, a plot could revolve around them starting a family. Hiccup and Heather could face difficulties in having children, like dealing with some sort of magical or environmental factor that is affecting their ability to conceive. Or perhaps they adopt a child from a troubled tribe and have to help the child adjust to their new life with them.

A power - hungry Viking who sees Hiccup's transformation as a threat to his own authority could be the main antagonist. He might try to capture Hiccup in his Night Fury form and use him for his own evil purposes, like trying to create an army of transformed creatures.

The main antagonist could be a jealous character who is envious of Bertha's unique features, like her 'big boob'. This character might try to use Bertha's hiccup problem against her, perhaps by making her hiccup in embarrassing situations to lower her self - esteem.