This depends on where the anger is coming from, or why the person is angry. If they are reacting from past trauma in their life, then a trauma-focused approach may be most effective. If they are just stuck in bad habits and repeating poor behaviors, then Cognitive Behavioral Therapy (CBT), Dialectical Behavior Therapy (DBT), or Psychodynamic Therapy may be most helpful. If the person with anger is deeply affecting their relationship, or their relationship is leading them to be angry, then couples counseling may be most helpful. If their anger came as a result of a major loss in their life, then Grief counseling may be the most appropriate approach.
You may not know where the anger is coming from or what approach you should take. In that case, just starting general counseling with a therapist would be a smart step. This way you can start working with someone. Then, as you describe the anger and what is underlying it, you and the therapist can discover the best approach at that point.