The best way in my opinion is to always be the example. When you discipline a child for doing something wrong it is best to make sure you are calm, patient and do not raise your voice or hit the child. A child learns by their surroundings. If a child has been surrounded by "anger", then that is usually what they will learn and use themselves. If they are surrounded by positive role models who have good problem solving skills then that is what they learn. Calmly remove the child from the situation and talk to him or her about being gentle, nice etc... Give examples of what nice and gentle are using a toy doll or stuffed animal. Pushing it or hitting it is not nice, hugging it is nice for one example. The child should catch on pretty quickly. If the bullying continues even after working with the child patiently for a few months then seek a professional counselor. There could be underlying causes for the child's anger that needs to be addressed.