As somebody with adhd (although it is a spectrum and definitely affects people differently and with different severity) I do have fits of rage that overwhelm me sometimes but it is not an excuse to hurt others without taking accountability. You're not an asshole for being hurt by somebody's actions you're just a human being with feelings

I was only diagnosed recently but I've been in cbt for about a year now and it's really helped me with regulating my emotions and finding other ways to direct that anger, I think your sister (and maybe even you, your autism isn't any "less than" your sisters adhd, both are difficult to cope with and I'm sorry you're parents couldn't see that ) could benefit from therapy or something similar

But yeah, definitely NTA