Another possible antagonist could be a sly fox. The fox might smell the unique lemons that Peter Rabbit is associated with and wants them for himself. He could try to trick Peter Rabbit into giving up the lemons by making false promises or threats.
Mr. McGregor could be the main antagonist. He might be jealous of the special lemons that Peter Rabbit has found and try to take them away. He could see the lemons as something valuable for his own use, like making a delicious and profitable lemonade.
It could be Orochimaru. He might be interested in the unique power of the rabbit Bjuu and try to capture it for his own experiments. He has always been after powerful entities in the Naruto universe, and this rabbit Bjuu would be no exception.
It could be Loki. Since Peter has lifted Mjolnir and become a new force to be reckoned with, Loki might see this as an opportunity to cause chaos. He could try to manipulate Peter or steal Mjolnir from him to gain power for himself. Loki's mischievous nature would make him a great antagonist as he tries to outwit Peter at every turn.
Well, perhaps Peter Rabbit finds a lemon that has fallen from a far - off land into Mr. McGregor's garden. This lemon has the ability to grant wishes. Peter Rabbit decides to use the wishes to make the garden a safer place for all the animals. However, he has to be careful as the lemon's magic attracts some unwanted attention from other greedy animals.
There could be an old - fashioned lemonade tycoon as the antagonist. He has a monopoly on lemonade sales in the area and sees Botan's new and innovative lemonade recipes as a threat to his business. So, he uses his wealth and influence to try and drive Botan out of the lemonade - making business, creating all sorts of obstacles for her along the way.
It could be a power - hungry nobleman who sees Sansa and Father Lemon's growing influence as a threat. This nobleman might try to undermine them at every turn, spreading false rumors and plotting against them.
It could be a super - powered being who has the ability to control lemons and make them do his bidding. He sees Elastigirl as a threat to his lemon - based empire and tries to take her out. He might have a gang of lemon - themed minions to help him in his evil deeds. He could be someone who was once wronged by the city and now wants revenge using lemons as his weapon of choice.
Perhaps a new, powerful and mysterious ninja who has a vendetta against the Hidden Leaf Village where Sakura is from. He sees Zetsu as an accomplice of the village and targets both of them, causing chaos and danger in their lives. This new character could bring in a fresh and unexpected element of danger to the fanfic.
It could be an evil sorcerer. This sorcerer might be after Noctis because of his special powers. He sees Noctis as a threat to his plan of ruling the world. The sorcerer could also target Iris because she has a pure heart, which he wants to corrupt, and Lemon because Lemon has a map that leads to a powerful magical artifact that the sorcerer desires.
A powerful water nymph could be the main antagonist. Maybe she's jealous of the special bond between Percy and Poseidon and the power of the lemon. So she tries to steal the lemon and use its power to take over Poseidon's domain.
It could be a rogue ninja who has a vendetta against Naruto and sees Sister Lemon as an easy target to get to Naruto. This ninja might have some special powers that make him a formidable foe, like the ability to control shadows in a more sinister way than Naruto's shadow clone jutsu.