I really lost my temper and gave my brother a concussion
I hope it was an accident. Why did you do that to your brother?
Because he was being a brat to me.
You should never hurt anyone, you will find yourself with serious consequences. You are especially expected to be nice to your siblings, regardless of how you feel about their behavior.
I'm thinking about to do it again because he didn't apologize for being brat.
It's a bad idea to follow through on that thought. You wouldn't want to seriously injure your brother would you? Hitting him with the intention of harming him is dangerous, and if you went overboard he could really get hurt.