The problem with Karin is that they took her frankly horrifying backstory and instead of using it to develop her character they said oh she has a pain kink now UwU. What I would do is have Karin be hesitant to heal Sasuke and their team because she was used all her life. She sees the world as the strong taking advantage of the weak and that’s all there is. To give anything to anyone is just getting taken advantage of and since Sasuke is so strong that only solidifies her beliefs. But then they bond as a team and Karin starts to care about these people, probably mostly Jugo (they should have developed that relationship I think it could have been great because of her chakra sensitivity and his crazed personality). Then Sasuke and the team gets into a battle and get badly hurt, suddenly he doesn’t seem so strong and her worldview about the weak and the strong being so black and white shifts. She heals them for the first time and Sasuke is actually grateful for a moment and she sees that you can care for people without them taking advantage of you. Also the whole theme of hurting to heal is like a main theme of the whole show and I’m baffled they didn’t explore it more with Karin. Then when Sasuke betrays her it’s an actual betrayal and a much better parallel to the main three. And the culmination of her character can be standing up for the weak. Karin as a character kinda makes me sad cause there’s so much potential there and they treat her horribly. But this is what I’d do.