Maybe a powerful demon that wants to use angewomon's power for itself. By transforming her into a keychain, it can control her movements and keep her in a weakened state until it figures out how to extract her power. So, the demon would be the main antagonist.
It could be a dark wizard or sorcerer who has a grudge against angewomon and decides to transform her into a keychain as a form of punishment or to keep her from interfering with their evil plans.
A powerful and jealous digimon who has always been envious of angewomon's status and power could be the main antagonist. They might have found a way to turn her into a keychain to get rid of her.
It could be a powerful dark wizard or sorcerer who has a grudge against angewomon or wants to use her power in some way, so they turn her into a keychain.
Well, perhaps it could be about a magical spell that changes angewomon into a keychain. Then the story might follow her adventures in this new form, like being carried around by different characters and experiencing the world from a tiny perspective.
Maybe the story could start with angewomon getting cursed by an evil digimon. This curse slowly transforms her into a keychain. Her friends then embark on a journey to find a way to reverse the curse. They might face various challenges and meet new digimon along the way.
In the 'angewomon was turned into a keychain fanfic', it could start with angewomon being caught off - guard by a strange spell. As a keychain, she is carried around by a human or another character. She can't communicate in the same way as before, but she tries to send signals. Her friends notice her disappearance and start to search for her. Along the way, they discover that the keychain has some special powers that could either be a curse or a way to break the spell. They have to figure out how to use these powers and find the source of the spell to change her back.
A powerful and jealous Digimon could be the antagonist. Maybe a Digimon that has always envied Angewomon's grace and power. This Digimon finds a way to turn her into a doll to get her out of the picture and claim her status in the Digital World.
Perhaps a group of anti - technology extremists could be the main antagonists in an Ultron fanfic. They see Ultron as the symbol of all that is wrong with technology and are determined to take him down, no matter the cost. They might use their own advanced, but more rudimentary, technology to fight against Ultron. This would create an interesting contrast between Ultron's high - tech abilities and their more basic, yet effective, methods.
The main antagonist could be a jealous acquaintance of Cosimo. This person has always been envious of Cosimo's status and charm. When he sees Cosimo falling for Contessina, he decides to sabotage their relationship. He starts by spreading malicious lies about Contessina, making Cosimo question her true nature.
An organization of rogue scientists who want to experiment on Pokemon could be the main antagonist. They might be trying to create super - powerful mutant Pokemon or find a way to control all Pokemon. If you're reborn as a Pokemon, they might capture you for their experiments. This could lead to a story where you have to escape from their labs and expose their evil plans to the rest of the Pokemon world.
A powerful, ancient sorcerer could be a great main antagonist. This sorcerer could have been locked away for centuries but has now broken free and wants to take over the universe from the Master of the Universe. He could have dark magic that the Master has never faced before.