Well, there is no one universal rule, at Polish universities there is huge autonomy of professors, so the teacher can personaly establish the requirements and dependable on the teacher it can be extremaly difficult or easy.
Don't be unfair, regular bribes aren't the big problem at the universities! The familly connections have much bigger influence on your professional perspectives, but it's rather during recruitment process to the PhD studies than during master studies. Unfortunatelly I have to agree that teachers' likes and dislaikes have huge influance on your grades.