People also seem to forget something.. this kingdom just finished a very long VERY costly war with the demon race. The king may have won the day but the damage was most likely astronomical. say for example 30% of the entire kingdom had casualties. Well at this point it would be practically impossible to rock the boat at the moment until the country is more prosperous because as other people pointed out. Taking on the people who have 1/4 of the budget for the kingdom is like declaring a civil war. and this country has already had enough of war for a while. He knows he legally can't do shit but he can give the unauthorized go ahead for an assassination of a corrupt noble to the worlds best assassin. Furthermore, he can't be that bad of a king considering that our MC is literally going outright to consult him on the problem. Plus.. killing the king would literally be killing one of his friend's dad... not exactly a nice thing to do to your friend.