Anger is often derided, yet it is an emotion indicating distress just as anxiety is. The roots are often in toxic experiences in early childhood. For that reason it is chronic and can take a lengthy time to reduce.
Treatment for anger looks at childhood experiences which predispose us to it and then adult experiences in which we are more likely to express it, often inappropriately and in a way which undermines us and others. Treatment is often on an individual and then group basis.