If he could get rid of the king, then perhaps he wouldn't have to kill anyone at all. Of course, that didn't mean that he was happy about having to murder someone, even if it was for the good of the country, but he knew that he had no choice.
The king wasn't weak, he could easily defeat his enemies. It didn't stop him from hating it, however. He knew that there was nothing he could do to change these unfortunate circumstances, so he resigned himself to the fact that there would likely always be blood spilled on his hands, which unfortunately meant that he had no choice but to...