they could remove Little Phat Un
What would that look like operationally? Fat Wun armed with nukes would be just as displeased with the Chinese for trying to unseat him as he is with the US. Back against the wall, those weapons could just as easily fly towards towards the Chinese with devastating consequences.
What magic weapon do the Chinese possess that will pacify chubby while simultaneously having him stand down? The Chinese are just as much at risk of NK's nuclear rath as everyone else.