One is allowed to use reasonble force against an attacker. Basicly it is up to the court to afterwards judge if you used reasonable or excessive force. So there is a chance that the victim will also be prosecuted along with the attacker.
There have been multiple cases in the newspaper where the victim also was prosecuted for using too much violence in self-defence.
We live in a socialdemocratic country where the police is supposed to protect you. But that is of course only a nice dream which does not work in reality.