Who could be the main antagonist in a Cybertronian Jack fanfic?

Perhaps a story where Jack discovers a hidden power within himself that has a connection to Cybertronian technology. This power could make him a key figure in a conflict between the Autobots and Decepticons. He might have to learn to control it with the help of his Cybertronian friends.

A corrupt police officer could be a great antagonist. He might be trying to frame Jack for crimes he didn't commit because Jack has been getting in the way of his illegal activities on the streets.

It could be Pitch Black. He might see the union of Jack and Elsa as a threat to his plans of spreading darkness. Their combined powers of ice and winter magic could be a powerful force for good, which he wants to prevent. So, he tries to create misunderstandings between them and stir up trouble in their relationship.

Perhaps a group of anti - technology extremists could be the main antagonists in an Ultron fanfic. They see Ultron as the symbol of all that is wrong with technology and are determined to take him down, no matter the cost. They might use their own advanced, but more rudimentary, technology to fight against Ultron. This would create an interesting contrast between Ultron's high - tech abilities and their more basic, yet effective, methods.

A powerful sorcerer could be the main antagonist. He might be jealous of Jack and May's emerging powers and see them as a threat to his own plans of ruling the land. So, he tries to stop them at every turn, creating various obstacles and sending his minions after them.

It could be an ancient ice - hating wizard. This wizard might have been banished long ago but now that Jack Frost has gone back in time, he sees it as an opportunity to stop winter from ever existing. He could use his dark magic to melt all the ice and snow in the past, which would have a ripple effect on the future.

Pitch Black would be a likely main antagonist. He could manipulate Jack Frost into turning dark, as he has a history of preying on the insecurities of the Guardians.

A new character could be introduced as the main antagonist. For example, a powerful ice sorcerer who is jealous of Jack Frost's natural ice powers. This sorcerer might have developed a special spell to freeze Jack's heart in order to steal his powers and take over his role as the bringer of winter.

Another option could be Zalgo. If he wants to expand his influence into the area where Jack and Toby are, he would see them as obstacles and try to eliminate them. Their combined efforts would then be focused on fending off Zalgo's minions and ultimately Zalgo himself.

A rival medicine cat from another Clan might be the main antagonist. They could see Alderheart as a threat to their own status or the well - being of their Clan. So they might use dark magic or some underhanded tactics to bring about his death.