My friend has anger issues, too. Here are some things that I did to calm them down in "angry situations": 1. Become the calm person. If you're resolved, look them straight in the eye, and act extremely calm, it might get to them and they'll wind down. But if they're super angry, they probably will just shove you off. Sometimes it's good to let the person cool off by themselves. Other people might just anger them further. 2. Don't get angry at that person. It'll make them feel cornered, and they'll go about hating the world. 3. Make them laugh. Laughter is the best medicine.
If that person has been told to calm down and that professional help is needed, but won't seek help, and if it is a boyfriend/girlfriend who abuses, either verbally or physically, don't waste your time or safety Run, don't walk away from the relationship.
Depends how close you are to them. If its a family member, you try to explain they need anger management, and if They don't get it, there could be consequences. If it a boyfriend, you can just dump them. If its a class mate or employee, you can just alert a teacher or boss, that you're worried. But it's hard to make someone realize things, unless they are willing to.
There is no need for you to deal with someone who has anger management issues. If a person brings me down, I do not associate with them in my life.
If you need to deal with this person in your family, I would ignore them and walk away whenever they start to lose control. If it is someone at work say "I can't talk to you like this right now. Please come talk to me when you have calmed down, or I will take it to HR for harassment."
This is not the kind of issue you should handle alone. Find professional help in area. From personal experience I have learned you cannot change someone who does not acknowledge that there is a problem.