In a school - based fanfiction, a bully could be the one who causes Christy to get hurt. The bully might push her down the stairs out of spite. This would then lead to the school authorities getting involved and the other students either standing up for Christy or being afraid to speak out against the bully.
Maybe in a fantasy fanfiction, an evil sorcerer is the villain. Christy might be a key figure in a prophecy to save the kingdom. So, the sorcerer tries to stop her by casting a spell that makes her get hurt. He doesn't want her to fulfill her destiny and will do whatever it takes to keep her from being a threat to his power.
One possible plot could be that Christy gets hurt during a sports event. Maybe she's playing soccer and gets tackled too hard. Her friends then rush to her side, and the story could focus on their reactions and how they help her. For example, one friend might call an ambulance while another stays with her to keep her calm.
A new emerging criminal who has a grudge against technology and those who use it to catch criminals. Garcia, being the tech genius, would be a prime target for them. They could plan an elaborate scheme to hurt her and disrupt the BAU's work.
It could be an ex - boyfriend who was jealous and wanted revenge. Maybe he couldn't handle the break - up and decided to harm her in this extreme way.
Maybe a malfunctioning android created in the lab could turn against Chase and be the main villain. It could accidentally cause him harm during a routine check - up or experiment, and then continue to pose a threat as it goes haywire and tries to prevent anyone from fixing the situation.
It might be an accident - causing character. This could be someone who is clumsy or irresponsible. Their actions, even if not intentional, end up causing harm to Judy. For example, they might accidentally start a fire in a place where Judy is, and she gets burned in the process.
Sometimes, it could be due to her own actions. Lydia might be overconfident and take risks that she shouldn't. For instance, she could try to perform a very difficult and dangerous magic spell without proper training, and it backfires, causing her to get hurt.
It could be a villain in the fanfiction. Maybe a new, powerful vampire who has a vendetta against Bella or her friends.
There are also the possibility of some inter - dimensional beings. In the Ben 10 universe, there are many different dimensions. If a being from another dimension comes through with the intention of causing chaos, they could target Ben. They might have powers that are completely foreign to Ben and his allies, making it difficult for him to defend against them. And let's not forget about the possibility of some of Ben's old enemies teaming up. If they work together, they could come up with a plan to really hurt Ben, whether it's physically or by ruining his reputation among the people he protects.
There could be a new character in the fanfiction, like a bully who targets Lincoln just because he seems like an easy target and ends up hurting him.
Another character who might be responsible is a jealous rival. This person could be envious of Elena's popularity or her relationship with someone important. So, they set a trap that causes her to get hurt.