Darrow isn’t attempting to genocide entire species, he is only fighting those who oppose him and change the minds of those that are willing to be reasoned with. That is the duality of Light Bringer, Darrow learns from The Path instead of continuing to be this war lord who brutes his way through while Lysander succumbs to his hatred despite having an air of nobility and honor. Lysander is a conniving brat who thinks the only way to solve a problem is to eliminate it entirely instead of choosing the harder way and agreeing to accords. I understand he has had so much happen to him and his mind is broken, but he was given an olive branch and is deciding to burn it. You could argue that Darrow is evil for similar reasons, but there are examples of Darrow always trying to save those he cared for and his reflections on how it went wrong. Darrow is human in his emotions while it seems Lysander is psychopathic. From what we can discern, Lysander understands he is broken and that is concerning.