Who could be the main antagonist in 'Jacob becomes a vampire fanfiction'?

It could be an old and powerful vampire lord who sees Natsu as a threat to his rule. Since Natsu is a new and different kind of vampire, the lord might want to eliminate him.

Perhaps a powerful vampire lord who sees Sookie as a threat to his power. Since she was once human and has connections to both worlds, he might fear that she could rally other vampires and humans against him. He could try to eliminate her by any means necessary, leading to a lot of action - packed scenes in the fanfiction.

Maybe Voldemort or his followers could still be antagonists. Even though Harry is now a vampire, Voldemort might want to use his new state for his own evil purposes or simply view Harry as a nuisance that must be destroyed. Since Harry has changed, he might have new weaknesses that Voldemort could exploit.

Another possibility is a vampire who wants to use Ethan for his own gain. He might try to manipulate Ethan into doing things that are against his will. This vampire could be part of a powerful vampire clan and wants Ethan to be his puppet so that he can gain more power within the clan.

It could be an old and powerful vampire who sees Hermione as a threat to his rule. Since Hermione is a very intelligent witch - now vampire - she might be able to figure out a way to undermine his power.

One idea could be that Jacob struggles to adapt to his new vampire instincts while still holding onto his old wolf pack values. He might have a hard time controlling his thirst around his former friends.

A powerful cult leader could be the main antagonist. The cult leader believes that the artifacts Lara and Jacob are after have some dark, magical powers that he wants to use to take over the world. He sends his minions after them, constantly trying to thwart their progress and capture the artifacts for his own evil purposes.

It could be another vampire clan. They might see Cartman and Kyle's relationship as a threat to their own power or way of life. For example, if Cartman and Kyle are trying to promote co - existence between vampires and humans, the other clan might oppose it.

A powerful elder vampire who opposes the prince's ideas of change within the vampire community. This elder might see the prince as a threat to the traditional vampire ways and will stop at nothing to undermine him.

Maybe a witch who has a vendetta against vampires in general. She could use her magic to cause all sorts of trouble for Edward, like casting spells that prevent him from using his vampire abilities or even creating illusions to drive him mad. Since she's a witch, she has different powers compared to a normal vampire hunter, so she'd be a very formidable antagonist. She might also be able to manipulate other humans or vampires to do her bidding in her quest to get rid of Edward.