“Unethical behavior” is kind of vague. If the HR department is competent, they probably don’t fire you for complaining about something actually illegal. Still, retaliating against employees for legitimate complaints about it ethical issues, or even well-intended but incorrect complaints, generally constitutes wrongful dismissal. Good luck on the job search, and find a lawyer to consult. I hope you have success on the wrongful dismissal suit!

If the story is true you have slam dunk case in Polish court for wrongful job termination. It's not USA, employees are protected.

You're not in America so you can actually do something about it. If you were in this country, you'd be screwed.

People have to get over the idea that HR is their friend. HR are the henchmen of top management shielding them from accountability.

If it was truly unethical like sexual harassment you should take legal action