Perform an action or say something (usually negative) by getting very close and
face to face with someone so they have to pay attention to you. It is intentionally intimidating.
While 'face to face' can be neutral or even natural, 'in his face' is aggressive, intrudes on
personal space, and usually does not allow the person an
escape route to avoid your action or statement.
'laugh in his face' means to laugh at someone, but not merely
participate in laughter; it means that you approach him, get his attention, and let him know that you are laughing at him.
'Get in his face' means to get someone's attention directly, offensively, by physically putting your face close to theirs when you are speaking. The intent is to
maintain his attention in such a way that he cannot look or
walk away.