Let me put is like this.  Attacking North Korea has a Human capital cost.  The main objective is to liberate the North Korean people and perhaps give the land back to South Korea.  It is in the best interests of Freedom to save them but it remains as to whether we are willing to pay the price.

At best an assassination attempt could destabilize the region.  It seems that the main figurehead Kim-Jong-Un is the main malefactor and removing him could be a first step to incentivizing rebellion in North Korea, both in the Civilian population and the Military complex.

There is also the idea of striking first, the U.S could immediately target there long rang missile capabilities and remove them first.|

A direct invasion would cause a lot of bloodshed, hence why NK sustains a Large Military Force

Things to think about moving forward.  Especially if WW3 is on the Horizon.