What do you think about me putting my sister outside and laughing at her?
Why would you put her outside and laugh at her?
She got what she deserves, she was very annoying at that time
Treating your sister like that is awful even if she's being annoying. You shouldn't put her outside and laugh at her, you could try either talking to her about her behavior or not paying attention to what is annoying you.
She is a brat and I never liked her.
It's wrong and cruel to mistreat your sister like that and laugh at her. You should consider the long-term effects that it will have on your relationship with her. By treating her like that, you are equally being a brat.