I've been working on a fantasy story and in a later installment I plan to really put my MC through the ringer but I wonder if there is every a line with that. In the story the villain gets his hands on a special stone that will increase magical potential in humans. He wants to use it to create an army of super soldiers but doesn't want to risk his men so he tells his soldiers to abduct as many villagers as they are able for the experiments, including the MC's hometown along with his parents. When our hero hears of this he knocks down every door and window of any soldier who will give him information. When he finally gets there, and fights his way through the guards to his family, he finds them to be mindless berserkers and his only choice is to cut down his own parents and everyone he's ever grown up with in the village. He finds the guy who lead the experiments and defeats him in combat but as the man is begging for mercy, the MC just starts to butcher him in combination of rage and despair, breaking his own code of never striking down a defeated man asking for mercy, something in a previous story he chided one his companions for. So needless to say afterwards he's very devastated. And he's 16 at this point. I'm wondering if the above situation is too cruel to the character or just necessary development?