I see Gamepress wiki still gives Nidoking a poor rating due to its best fast move being legacy Fury Cutter. There’s only one problem with that…it’s not true. Double Kick has since been added and it’s a major upgrade for the King.
Both moves get 4 EPT (a necessity given Nidoking’s low bulk), but DK has significantly higher damage output, plus Fighting is more useful than Bug as an offensive type.
The difference is good enough that if you have a Nidoking with Fury Cutter, you might want to TM it since you probably won’t need it anymore…ever.
Compared to Fury Cutter, Double Kick pairs more effectively with Sand Tomb due to its better damage output. Fighting and Ground also overlap somewhat on offense, due to Rock and Steel being weak to each. The DK+ST combo works great against “Steel tanks” like Bastiodon, and to a lesser extent Dark and Normal-types. It also offers decent counter-coverage against Ice.
For its secondary charged move, you can go with either Earth Power (for additional Ground oomph), Megahorn (for counter-coverage against Psychic and additional power against Dark), or even Sludge Wave (more expensive, but hits very hard with STAB, and provides coverage against fliers and fairies).
Nidoking is still something of a glass cannon, but it’s a lot less glassy than (say) Gengar. Between the addition of Double Kick to Nidoking and Poison Fang getting nerfed, it’s possible the King may be as good as the Queen now, if not better.
Nidoqueen is still definitely better against Fairy-types, but Nidoking is far better against Steels, so which one you should choose depends on the purpose you need it for.