At this point, just assassinate King Jung Un, bomb his top military leaders locations and hit any nuclear/missile sites we deem ready at a moments notice. Shock and Awe 2.0 hit it all at once and have a fully manned carrier group and South Korean army on standby ready to fight back at the DMZ. We can take care of air and naval operations and let the SK army take care of ground ops.
The only issue here is if there is any serious push for military action in NK then China will get involved militarily. They don't want another pro US country on their border.