Probably a joint-operation by the RoK, Japan, and the US.

For months Allied forces have been training to do what should have been done to Hitler in 1938.

The RoK has stressed that they are prepared to kill Kim if he continues to threaten SK.  Japan's leadership has described Kim's reckless provocations and threats as being completely "unacceptable."

President Trump is on record the about the benefits of killing Kim.

The RoK's Taurus missiles might be one means as might Tomahawk missiles from an Ohio-class submarine;
Japan has cruise missiles which they could launch from their fighter aircraft.

Kim is much worse than Hitler and he needs to be killed sooner rather than later.

President Trump will spend next week garnering international support for that mission at the UN and elsewhere.

A key question is: "How will Russia, China, and Pyongyang react to Kim's assassination?"

Should you have any pertinent, specific, well-foundled thoughts about this thread do let us know. (and GMD?!)