Can I punch my grandma?
What do you think you could gain from this?
I need to do it because she deserves that and I would stop thinking about her.
It is bad to punch elderly people because you can hurt them. If you feel the need to be violent you should seek mental help for dealing with your anger.
I'll punch my grandma.
There is never a good reason to harm an elderly person at all. I believe you will get caught for this and may also go to jail.