There is a huge difference between leading men in battle and them dying,
and deliberately finding ways to get them killed either by encouraging suicidal reckless behavior, conspiring a way to increase casualties.
Then of course, wanting some treasure or money is not evil, if people did die due to being indirectly murdered due to a conspiracy, Mathilde is guilty by inaction, aand guilty of not performing her duties to protect the empire and it's people.
What is ethical in war is completely different from what is ethical anywhere else. I once was able to watch an ethics panel discussing the ethics of war with officers of the Military, trained in the ethics of war and what is and is not appropriate. The discussion was startling.
When an officer was asked what he would do when his unit was asked to charge an encamped enemy and a member of his unit disobeyed and began creating dissension within the ranks, the officer had an answer. The man would have one chance to change his attitude, and if that did not work it would be an immediate execution on the battlefield.
The answer was sudden and brutal and surprised a great number of the non-military ethics panelists. The officer explained that discipline was paramount, and orders need to be followed when given. Dissension in the ranks is not allowed, and when you are on the battlefield there is no time or place for less extreme measures.
Codrin is in a similar position. He is in charge of a large section of the adventures and vagabonds who need to follow their orders or risk the entire expedition. However, in the middle of nowhere it is next to impossible to get rid of the troublemakers in a less extreme method without causing morale problems in the ranks. Nobody wants to throw their friends in the brig and guard them. They're also not going to simply leave when requested, or even when ordered. Codrin did what he thought was needed to get rid of those that would spread dissension and were troublemakers.
Were his actions morally reprehensible? We don't know exactly what he did, but it is likely they were. Even for wartime morales. But whatever the morality of his methods, the mercenaries held. They held the line and pushed back the Greenskin tide, saving their own lives and the lives of countless archers and cannon crews. And at the end of the day, that is what they needed to do.
Warhammer is filled with bad people doing bad things for good reasons. Compared to witch hunter purges of innocent villagers to cut a cult out by the roots, military generals ransacking entire towns to feed their armies to beat back the hordes of enemies, and even the Grey Order's torturers pulling threads of information from reluctant lips, Codrin's actions are relatively tame.
We don't have to like it, and we probably shouldn't like it, but the Warhammer world is a brutal world that does not allow for half-hearted measures in the middle of Greenskin territory.
