When it comes to raising a non-angry child, we should know how to teach our child how to control his negative emotions and feelings: we should never wait for bad situations which make our child angry to appear.
We should know that the best we can do is to take the initiative and try to create as many opportunities as possible in order to teach him how to cope with negative emotions - psychologists name these teachable moments.
If you do not know how to do that, we can give you some ideas: when you play a game with your child, do not let him win - you can see his reactions and you can also speak with him about these reactions - ask him how he feels when he loses, if he is angry, how he believes that other angry people feel.
There are no right or wrong answers.
The most important is to have this discussion with him and make him realise that we all get angry from time to time, but we can also control our anger! Present to your child a situation in which some principles are violated - try with honesty and fair play - have a discussion about these principles, about how he thinks that a person who is being treated unfairly feels, if he thinks that this person gets mad and if that person's anger is justified.
Ask him what he believes about this situation and how he would solve a situation like this.
This way, you can teach your child that anger is something normal, but, at the same moment, that anger should not control us - we should control it!