You find out where that kid lives. Go to their town and tell them of how brave their father was and how he died next to you in battle fighting the enemy hordes. Tell him you made a promise to raise him and see to his education. Add child to raiding party. Raise him to be a merciless avenger in his father's memory. Become the scourge of the continent. Eventually child finds out that you were the one who killed his father and turned him into a monster for your own profit. Meet child on the plains for a final battle. Refuse to lift your sword in defense because you've come to love him as your own. Oh no - the whole thing was a setup by the enemy: they leaked the truth to the kid and set up this meeting as an ambush for both of you, hoping you'd kill/weaken each other. Fight to your dying breath defending the kid and helping him escape. Last words your hear as he escapes and leaves you to your fate are about how much he'll miss you and forgives you.