What is the ruling on exposing an individual among his colleagues or boycotting him if he is spreading discord and pursuing personal interests, especially if the administration supports him?

If a person is stirring up discord (fitna), you should first advise him and warn him of the consequences of his actions, explaining the impermissibility of what he is doing. If he does not respond, then warn people about him. If you are an employee of the management and there is negligence from some workers, you should advise the negligent person. If he does not respond, report him to the management. However, beware of wronging anyone or submitting a false complaint.