Help me !

My 10 month old has been really mean lately . He pulls my hair and slaps people all the time . My SO plays rough with him and I really believe this is the reason anyways I have no idea how to tell him this is not okay . I take his hand when he does this and he just laughs . My SO on the other hand slaps his hand and I just feel

Horrible. Please if you guys have gone through this and your LO stopped how did you do it and what did you do ?

Desperate Mom