If you have ever know anyone with anger issues, you know how scary it can be. I am talking about people who smash things or threaten or hurt you. Big time anger issues. It seems like most of the guidance one gets on this is learning to stay calm or subdue anger. The old count to ten idea.
Most people who have anger issues aren't perpetually angry. Anger blows like a storm. Anger is an emotion. Emotions aren't wrong. Emotions are part of who we are. But, still most people would answer that the opposite of anger is calm. Most anger training has to do with self control. I have known people who were calmly angry. Seething is the word I would use for that. Calm controlled anger leads to revenge or getting even in many cases in my experience.
I heard a priest on the radio talk about the opposite of anger the other day as I was driving around. He said that the opposite of anger isn't calm, it is caring. What an epiphany. Caring. If you care about someone, you wouldn't smash something, scream at them, threaten them or hurt them. I thought about road rage, and took it to the conclusion that if someone angered me, it was my job to care about that person. Whatever the reason for the bad driving, they needed my prayers and my care.
The opposite of anger is caring. Not an easy practice, not easy at all, but in many ways, better than control or calm anger. Care about the source of the anger. Care.