I've never been a fan of 'wiping out' a realm. Smashing their army, see their council driven before you, and hear the lamentation of their peasants...sure. If you can beat them, then chances are you don't need all their regions.
Even if they are reduced to just a Capital and a few rurals, let them keep their lore/realm if players want to keep it. You don't have to own the whole map to win. Honestly, if a good realm is being snuffed out, everyone loses. Even the realm who conquers the map.
