On the issue of Simeon and Levi killing all the men of Shechem, there’s rabbinical debate regarding whether or not it was justified.
According to the Noahide laws (a binding moral code for all Gentiles), the penalty for Shechem’s violation against Dinah is death, and the penalty for allowing such actions is also death. Therefore, it was a righteous slaying.
On the other hand, Shechem was a prince. Who could possibly stand up to him? Only Shechem was guilty. Therefore, it was unrighteous.