I only have Barred Rocks and they push each other around like crazy! I let chickens be chickens but I did scold one of the girls for being a bully. She tried to look innocent but she had a pin feather in her beak so I wasn't buying her act.In our experience, RiR and Plymouth Rock are the more dominant breeds. They are sweet birds but our Barred Rock have been the bigger bullies to other hens and Leghorns have been the more food aggressive towards other hens even though they are the smaller hens.
Others might have different experiences with other breeds.