I find this scene very interesting: the dichotomy Murad creates between his "brother" persona and his "sultan" persona. This is something recurring with sultans, as it allows them to deal emotionally with hurting (or even outright killing) their family members (or even others): it's a form of compartmentalization that they need to cope with the amount of power they have over others and the decisions they have or feel like they have to make in order to keep that power.
What stands out to me here is that Murad seems disturbed by his lack of remorse, and it's this lack of remorse he feels sad about it, and not the fact that Kasim himself is hurting. He makes the whole thing about him: "I punished myself, not him." I feel like this is a mark of egomania. Instead of thinking about what Kasim is going through, he's like: "I don't feel. This hurts me. Therefore, I am the true victim." It's more about a narcissistic injury of having betrayed his self-image as a just and righteous person, but also of not being able to remain the loving brother he once was, the child who would use a wooden sword to defend his brothers. Those were dangerous times, but at least they had each other, and he didn't have all these responsibilities, all this power that changed him for the worse.