Perhaps a group of bandits could be the main antagonists. They spot Link dressed as a girl and think he's an easy mark. But when they realize that Link is actually a very capable fighter, they become determined to take him down. They start hunting Link, causing him to constantly be on the run and having to use his wits and skills to survive while still in his female disguise.
The main antagonist could be an alien who has a vendetta against Ben specifically. This alien might be able to sense Ben's true identity even when he's dressed as a girl. He could try to expose Ben and foil his mission or just cause general chaos while Ben is in his disguised state.
Ganon could still be the main antagonist. His motives remain the same - to take over Hyrule. But now he might underestimate Link because she's a girl, which could be his downfall.
Ganon could still be the main antagonist. Even though Link has turned into a girl, Ganon's goal of taking over Hyrule remains the same. He might underestimate Link in her new form, which could give Link an advantage. For example, Ganon might not expect the girl - Link to be as strong or resourceful as the male Link, but she proves him wrong.
The main antagonist could be the head of the CIA operation that orders Link's kidnapping. This person might be power - hungry and believe that Link can be used to gain more control or knowledge.
It could be an envious rival. Maybe there's another girl who is jealous of Pyro's unique abilities or charm. She constantly tries to undermine Pyro and create obstacles in her path.
A jealous witch could be the main antagonist. She sees the Sunlight Girl's popularity and power, and out of envy, she tries to cast dark spells on the girl to dim her light.
Perhaps a character who is allergic to balloons and wants to ban all balloon - related activities in the town. This would put the balloon girl in direct conflict with them as balloons are her passion.
It could be an envious classmate. Let's say Hope is really good at academics and is always getting top grades. This classmate, out of jealousy, starts spreading rumors about Hope, trying to isolate her from her friends and undermine her confidence.
It could be a new villain who is specifically targeting Gohan because of his new form. This villain might see Gohan's transformation as a sign of weakness or an opportunity to mess with the Z - fighters. Maybe they want to use Gohan's confusion and the chaos it causes among his friends and family to their advantage.
It could be someone who wants to take advantage of Minato's new female form. Maybe a villain who has a vendetta against Minato in his original form and sees this as an opportunity to further humiliate or harm him.