In the EU, how much protection do I have if I report an assault on myself by my department head?
If the matter has escalated to a physical assault then you have the option to contact the police.  For lesser issues concerning corruption or maladministration of public resources, you should consider searching for the closest equivalent of an ombudsman for your university sector.  In public industries with an ombudsman it is usual to be able to make a report of maladministration or corruption, and there are protections for whistle-blowers who file reports on these matters.  Specific rules vary according to the laws of the country and the specific industry ombudsman, so you should first check to find the appropriate ombudsman and check the protections for whistle-blowers that apply in your case.  If you have a lot invested it is probably also a good idea to speak to a lawyer to get advice on the available reporting mechanisms and legal protections.