Who could be the main antagonist in Draco meets Andromeda fanfiction?

The Dursleys could also be antagonists in a way. If Draco comes to their home with good intentions, they might not believe him and be hostile towards him. Their over - protectiveness of Dudley and dislike for anything magical could make them oppose Draco and any interaction he tries to have with them.

The main antagonist could be a group of dark wizards who are trying to revive an ancient and powerful dark magic. They believe that Draco has some information about it because of his family's past associations. So they chain him up to force him to talk. This group could be led by a mysterious figure who has a personal vendetta against the Malfoy family.

Maybe a powerful warlord from Negan's world who somehow follows him into Artemis' realm. This warlord, with his own thirst for power and destruction, would oppose both Negan (if he starts to side with Artemis) and Artemis herself, wanting to take over the new world he has found.

It could be another god who is jealous of Zeus' interest in Atreus. Maybe a god who feels that Atreus is an outsider and doesn't belong in their divine affairs.

Another possibility is that Death is being controlled or influenced by a greater cosmic entity. In this case, that entity could be the main antagonist. It uses Death as a tool to test or destroy the Avengers. The Avengers would then have to not only deal with Death but also find a way to face this more powerful and mysterious entity behind Death's actions.

Kingpin could be a great antagonist. He has a long history with Daredevil and his presence in Hell's Kitchen could draw Peter in. His criminal empire and power would pose a significant threat to both heroes.

A powerful Decepticon could be the main antagonist. Maybe a Decepticon named Shockwave who is on a mission to find Bumblebee and extract some important information from him. He sees Dante as an annoying obstacle in his way and tries to eliminate him. Shockwave's advanced weaponry and cold, calculating nature would pose a great threat to Dante and Bumblebee's friendship and their goals.

It could be a dark wizard who wants to capture Nagini for his own evil purposes. Maybe he wants to use Nagini's connection to Voldemort to gain power.

It could be Orochimaru. He might want to use Ino's connection with the Kyuubi to his own advantage. Maybe he plans to extract the Kyuubi's power through Ino's mental link with it.

It could be someone who wants to steal Samehada for its power. Maybe a rogue ninja who has heard of Samehada's ability to absorb chakra and plans to use it to take over the ninja world.