It could be a powerful sorcerer. In the Dark Skies world, a sorcerer with dark magic could oppose Jesse. This sorcerer might be after the same magical artifacts as Jesse or simply wants to rule the Dark Skies with an iron fist.
A warlord from a rival faction could be the main antagonist. In the world of Dark Skies, different factions might exist. A warlord from one of these factions, who is jealous of Jesse's growing influence or the resources they possess, decides to go after them. This warlord has an army at their disposal and is not afraid to use force to get what they want.
Perhaps a corrupted spirit. In the lore of Dark Skies, there could be a spirit that has been tainted by negative energy. This spirit sees Jesse as a threat to its plans of spreading chaos and destruction throughout the Dark Skies. It uses its supernatural abilities to try and stop Jesse at every turn.
One idea could be Jesse exploring a new, mysterious land in the Dark Skies world. Maybe they discover a long - lost civilization or a powerful magical artifact. Another plot could involve Jesse having to team up with an unlikely ally to face a common threat that looms over the Dark Skies. For example, a fearsome beast that is causing chaos.
An ancient evil entity that was once locked away could be awakened by Jesse's wither sickness. This entity doesn't want the sickness to be cured because it plans to use it to spread darkness across the Minecraft world. It starts to manipulate other mobs and characters to stop Jesse's friends from finding a cure.
Perhaps a group of dark side cultists could be the main antagonists. They idolize the power of the dark side and see Ahsoka as a prime candidate to join their ranks. When she refuses at first, they start to hunt her down, but in the process, they unknowingly push her closer to the dark side, creating a complex dynamic where they are both the pursuers and the inadvertent cause of her fall to the dark side.
The Green Goblin could be a great main antagonist in a dark fanfiction. He could be even more deranged and have a more elaborate plan to destroy Spider - Man, not just physically but also mentally by targeting his relationships.
It could be an unknown ninja who has been secretly studying dark energon for years. He wants to use it to take over the ninja world, believing that the power of dark energon will make him invincible.
Well, obviously Dark Gaia itself could be the main antagonist. It has the power to cause chaos and destruction, and Sonic would have to stop it from wreaking havoc on the world.
It could be a rogue Dark Jedi who has escaped from his own Order and sees the Naruto world as a new place to spread chaos. He might be seeking powerful chakra sources to fuel his Dark Side powers.
It could be Sasuke. If Sasuke continues to pursue his own vendetta in a more extreme way and Naruto's attempts to bring him back fail, Sasuke could become the main antagonist. Their rivalry could turn into a full - blown battle for power and ideology, with Naruto being pushed to his limits and potentially turning dark in the process of trying to stop Sasuke.
It could be an ancient dark wizard who has been manipulating events from the shadows. This wizard might see Elsword as a powerful tool and has been slowly influencing him to turn dark. The wizard could be using dark magic to cloud Elsword's mind and make him more susceptible to negative emotions.
Perhaps it's one of Percy's former friends who has turned against him. This friend could be jealous of Percy's powers or has been influenced by some dark force. Their actions and taunts could be what drives Percy to become dark, making them the main antagonist in the story.