Alec would be more practical. He'd assess the situation quickly, figure out the best way to get Clary to safety and medical help. He might also start investigating who or what was behind her getting hurt, using his skills as a strategist in the Shadowhunter world.
Simon might be in a bit of a panic. Since he's her friend and also not as used to the dangerous situations as the other Shadowhunters. He'd try to do whatever he can to help, like getting help from more experienced Shadowhunters or trying to comfort Clary while she's in pain.
The other characters' reactions can vary. Pixal, if she's around, would use her technological knowledge to see if there are any internal damages to Jay, especially if it's related to his electrical components. The villagers of Ninjago might also show their support. They could bring food or offer shelter for Jay to recover. The reaction of the villains would depend on the situation. Some might see it as an opportunity to finish Jay off, while others might be impressed by his courage in getting hurt while fighting them.
She might have to take a break from training. This could set her progress back. Maybe she'll feel frustrated and more determined to get better once she recovers.
Kagome usually gets very worried. She'll immediately try to use her spiritual powers to heal him if she can. If not, she'll search for herbs or other ways to help. Miroku would likely offer his support in a more practical way, like finding a safe place for Inuyasha to rest. Sango might be on guard, making sure that no more enemies take advantage of Inuyasha's weakened state.
Raph usually gets really angry. He blames himself for not being there to protect Leo or he gets mad at the enemy who hurt Leo. He'll be the first to want revenge and will be very protective of Leo while he's injured.
Yuki would likely be very concerned. He has a soft spot for Tohru and would probably rush to her side, trying to find a way to help. He might even blame himself if he thinks he could have prevented it. Kyo, on the other hand, would initially be angry, but that's just his way of showing worry. He would be more hands - on in getting her the help she needs.
The other characters' reactions can vary greatly. Some of the more powerful characters might see Atem's injury as a sign of weakness and try to take advantage. However, his true friends would rally around him. Bakura, in his good side, could offer some knowledge about ancient healing spells. Tristan would be the one to stand guard and make sure no further harm comes to Atem while they search for a solution. And the spirit of the Millennium Puzzle might also be actively involved in trying to heal Atem or guide the others on what to do.
Anakin, if he's in the story, would likely be very protective. He might rush to her side immediately, using his skills to try and heal her or at least stop the bleeding. His reaction could be full of anger towards the cause of her injury, vowing revenge.
In some fanfictions, Clary might get hurt because of a betrayal within the Shadowhunter community. For example, someone she trusts might lead her into a trap where she gets injured. It could be a complex plot where the betrayer has their own motives, like jealousy or a desire for power. This would not only physically harm Clary but also emotionally shatter her trust in those around her.
Jay would probably be very vocal. He'd be shouting for help and freaking out a bit. Kai would be angry at whoever or whatever hurt Zane and be ready to fight back immediately. Lloyd, being the leader, would try to stay calm on the outside but be very worried inside and start coming up with a plan to help Zane.
Thorin would probably be very concerned. Since Bilbo has become an important part of their group, Thorin might feel responsible for his safety. He could order the others to help Bilbo immediately and make sure he gets proper care.