As a manager, you will not always be dealing only with pleasant matters. You are obliged, amongst other things, to detect if the behaviour of any team member goes beyond certain limits, interferes with the work of others, insults them, intimidates them, stresses them out or is in any way uncomfortable for them. If there is someone in your team who tends to intimidate, exploit or even bully other people, you must act immediately. Here is a manual on how to do it.