Who could be the main antagonist in 'harry potter champion of death fanfiction'?

Perhaps an old follower of Voldemort who was in hiding. This person finds out about the Eyes of Death and believes that with their power, he can bring back Voldemort's legacy even stronger. He becomes the main force against Harry and his friends throughout the fanfiction.

Perhaps a dark wizard who is jealous of Harry's new power. This wizard could be someone who has long been in the shadows, waiting for the right moment to strike. He might see Harry as a threat to his own plans of taking over the wizarding world.

It could be Voldemort who somehow follows Harry into the Pokemon world. He might try to use the power of Pokemon to regain his strength and take over both the wizarding world and the Pokemon world. His dark magic could corrupt some of the Pokemon, turning them into his minions.

It could be Voldemort who somehow follows Harry into the DC universe and teams up with some of the DC villains like Lex Luthor. Their combined evil intellect and power could pose a great threat to both Harry and the DC heroes.

It could be Voldemort who somehow manages to extend his reach into the ROTG world. Since Harry is the master of death, Voldemort might see this as an opportunity to gain even more power and immortality. He could team up with some of the villains from ROTG, like Pitch, to create chaos and try to defeat Harry once and for all.

It could be a dark wizard who wants to steal Harry's power of being the Master of Death. This wizard might believe that with that power, they can rule the wizarding world without any opposition. He could be an ancient dark wizard who has been in hiding for centuries and now sees Harry as the key to ultimate power.

Perhaps an ancient spirit that has been awakened by the imbalance in the life - death cycle due to Harry becoming the Master of Death. This spirit sees Harry as the cause of the chaos and tries to destroy him to restore the balance in a way that is harmful to the wizarding world.

It could be Voldemort still. Even if Harry becomes associated with death, Voldemort is the ultimate symbol of death and destruction in the wizarding world. Their battle could take on a new dimension as Harry now has a different relationship with death.

Hermione Granger is another potential main character. Her intelligence and quick thinking would be invaluable in any competition or quest in the fanfiction. She could be the strategist behind the 'champion's champion', guiding them with her vast knowledge of magic and spells.

It could be a Death Eater who has infiltrated Hogwarts and is trying to use the Tournament to harm Harry. They might manipulate the events of the Tournament to put Harry in more danger than the other champions.