I'm going to slap my brother's face in front of his friends
Why do you want to do that?
He's been very mean to me lately
I'm sorry he's treating you like that. Siblings should be treating each other with respect! That being said, you should never respond to stuff like that with violence, which is wrong.
I'm going to do it anyways and I'm going to record his reaction.
That would only make him more angry with you. He would seek out revenge and be even more mean.