Dear
Welcome to HCM
We understand your concerns
I went through your details. Usually anger is due to irritation. Irritation can be due to frustration or disturbance from others.
Stress is another factor with which people do become short tempered. Over and above, a sort of low self esteem and low self confidence also triggers anger and aggression. Before advising the method to deal with the client, we would like to know more information about the client. We need to assess the dept of the client's anger. Is it just anger as an emotion is anger disorder? proper assessment of the client would provide the necessary insight.
Emotional anger and aggression can be approached with the help of
anger management therapy and slight life style changes with awareness. Anger disorder, most probably, could require treatment with the help of a
psychiatrist and
psychotherapy. I strongly suggest you to advise your friend to
consult a psychologist personaly or online. The problem can be cured, for sure.
If you still need my assistance in this regard, please use this link. http://goo.gl/aYW2pR. Please remember to describe the whole problem with full detail.
Hope this answers your query. Please feel free to post follow up queries. Available for further clarifications.
Good luck. Take care.