When you younger sister hit, kicks and scratches you make sure to tell your mom or dad. Also, try talking to her and ask her if she would like you to treat her like that, she should be saying "no". Once you have asked her that explain to her that she should treat people the way she wants to be treated a make sure to let her know how much it bothers you that she treats you this way, let her know that it hurts your feelings.
If your younger sister is hitting, kicking, and scratching you all the time, and you have asked her to stop but she won't, you need to tell your guardian/mother/father. Explain to your sister that she is hurting you and that she shouldn't be doing that to you or anyone else.