Who could be the main antagonist in a Danny Phantom Mystery Skulls crossover fanfic?

A plot could revolve around a new villain who has the power to manipulate both ghosts and the strange artifacts that the Mystery Skulls often deal with. Danny, with his ghost powers, and the Mystery Skulls, with their unique skills and knowledge, have to team up to stop this villain from achieving their evil goals. For example, the villain could be trying to open a portal that would merge the Ghost Zone with the Mystery Skulls' dimension in a catastrophic way.

Perhaps an organization made up of both Pokemon world villains and some of Danny's foes. They could be working together to create a portal that would merge the two worlds in a way that benefits them. They would be the main antagonists as they cause all kinds of chaos, stealing both Pokemon and technology from both worlds to achieve their goals.

The main antagonist could be one of the powerful and malevolent entities from 'The Suffering'. For example, the big bad demon or the tortured soul that has been corrupted by the darkness of that world and now wants to spread it to Danny's world.

Maybe a human hunter from Danny Phantom's world who has somehow found his way into the Ice Age. He has advanced weapons and a cruel nature. He starts hunting the Ice Age animals for sport and also wants to capture Danny Phantom because he sees Danny as some sort of strange, valuable creature. He teams up with some of the less friendly Ice Age creatures to achieve his goals.

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.

The combination of two distinct universes makes it unique. Mystery Skulls has its own set of characters with their own powers and personalities, and Danny Phantom also has a rich world of ghosts and superpowers. When combined in fanfiction, it creates a whole new set of stories and interactions that you won't find in either of the original works.

A new and powerful ghost that Danny has never faced before could be the main antagonist. This ghost could have unique powers that Danny isn't prepared for, and in their first encounter, it manages to defeat and kill Danny. This would set the stage for a story of revenge or trying to bring Danny back.

In the 'danny phantom is a lion fanfiction', the main antagonist could be a group of anti - phantom scientists who capture Danny when he's in lion form. They want to study his unique physiology and use his powers for their own evil experiments. They see him as a threat to their control over the human - ghost interactions and will stop at nothing to keep him locked up and experiment on him.

A new, powerful ghost that hates the Christmas cheer could be the main antagonist. This ghost could be spreading gloom and trying to cancel Christmas in Amity Park. Danny would have to figure out the ghost's motives and stop it from ruining everyone's Christmas. For example, it might be a ghost who was once a Scrooge - like figure in life and now wants to make others as miserable as he was.

It could be Sam and Tucker. Since Danny has become a villain, his former friends would likely try to stop him. They would be the main antagonists from Danny's point of view now. They would use their knowledge of Danny and their own skills to try and bring him back to the good side.