Who could be the main antagonist in a 'Danny Phantom becomes villain' fanfiction if Danny is the villain?

In a 'Danny Phantom becomes villain' fanfiction, it could be that Danny has a major falling out with his friends and family. He feels betrayed and abandoned. This emotional turmoil causes him to snap and turn to the dark side. He then uses his ghost powers to take revenge on those who he thinks have wronged him, becoming a feared villain in the process.

The main villain could be an older and more powerful version of Vlad. Maybe he has finally perfected his cloning techniques and created an army of half - ghost clones. He could be more devious and have a grand plan to take over both the human and ghost worlds.

A powerful warlock who wants to harness the powers of both Danny and Carrie for his own evil purposes. He could be an ancient being who has been waiting for the right time to strike when both Danny and Carrie are at their strongest.

Vlad Masters could easily be the main villain. Since he already has his own ambitions and a certain amount of power, in a royal - themed fanfiction, he could be trying to take over the ghostly royal throne. He might see Danny as a threat to his plans, especially if Danny has some newfound royal status, and thus plot against him.

Perhaps a rogue ghost who has managed to hack into Cybertronian technology. This ghost, let's call it Techno - Ghoul, has the ability to possess and control Transformers. He starts causing chaos by making Autobots and Decepticons fight each other. Danny Phantom has to use his ghost - hunting skills and his knowledge of both the human and ghost worlds to find a way to exorcise Techno - Ghoul from the Cybertronian systems.

The Guys in White could be the main antagonists. If Danny becomes evil, they might see this as their chance to finally capture and experiment on him. They would be constantly chasing him, which would make Danny see them as the main obstacle in his new evil plans, and thus they would be the antagonists in the story.

Perhaps a mad scientist from Danny's world who has somehow gotten access to Ultraman technology and is using it to create chaos. He could be creating mutant creatures that are a threat to both the Ghost Zone and Ultraman's world, and Danny and Ultraman have to stop him before it's too late.

A group of human hunters who have decided to target Danny's ghost side could be the antagonists. They might be trying to capture Danny and use him for their own experiments. Danny, feeling violated and angry, decides to take revenge by using his ghost powers to outwit them at every turn, and expose their cruel intentions to the people of Amity Park.

One great 'Danny Phantom' villain fanfiction is 'The Dark Reign of Technus'. It delves deep into how Technus could take over the entire town's technology infrastructure and turn it against everyone. The way the author describes Danny's struggle against this high - tech tyranny is really engaging.

A possible main villain could be a dark wizard from Star's world who has somehow gained the ability to control ghosts. He could use this power to try and take over both Danny's world and Star's, seeing the combination of magic and the ghost zone as a means to ultimate power.