Honestly, im starting to wonder how many people here actually had siblings growing up. You do dumb shit from time to time....like, REALLY dumb shit. One time my brother put a drink on the ground and i accidently hit it with my leg, spilling it all over the floor. He didnt want to clean it up, i didnt want to clean it up, so we got into a physical fight until we realised we were being kinda stupid and stopped.

That being said, there is no doubt that what OP did was far beyond any reasonable altercation; punching someone in the face and kneeing them in the stomach is pretty fucking nuts to do to your own sister. As such, allthough i dont agree with it personally, she is very much entitled to cutting off contact with OP. And OP is in no way entitled to forgiveness.

But OP, i'll give you credit where its due, i think you did a hell of a job trying to reconcile and an even better job giving her the space to go to family events etc. But yeah, its obvious the letters and all that jazz is meaningless, time to call it a game buddy.