North Korea has been preparing well to finish the south scum off
They've been preparing very very poorly, like a person who pays every penny he can afford to abate his debt but it still grows larger due to interest. This isn't for lack of will, but because they were economically choked off due to their extreme emnity towards the US and west (for good reason, of course). North Korea spends 25% of its GDP on the military but it's still falling behind South Korea's <3% spending every day on military tech. Everywhere else is a run-away for South Korea. North Korea can't afford any new jets, still flies Chinese J-5 with some barely maintainable old MiG-29 as their top fighters to defend Pyongyang. South Korea has swaths of F-16, F-15, F-35, and they're now designing their own 5th gen fighter. They started at the same place after the end of the Korean War. This shows exactly why burying yourself in hate when you are at a low level is counter-productive. Lots of Chinese may, for idolizing a US that antagonizes China, seem spineless especially compared to North Koreans who would rather go on a suicide mission before shaking an America's hand. But some of those Chinese people went abroad to humbly learn and they brought back the technology to turn China into a true competitor against America while those North Koreans can't produce results for their country.
and checkmate the US militarily.
That's literally impossible for North Korea. They would have to invent a new tech that can deflect all American nukes while getting hypersonic nukes themselves. They are too poor to even keep up not to mention jumping ahead.