That Nidoking is pretty good. Nidokings, after about level 40, start to become weaker than other Pokemon you could have. Unless you teach that Nidoking some better moves, I would suggest getting rid of it for their stats aren't very pretty.
It depends on what the stats are for it and what you think is better.
#5 - Fantina - Hearthome CityDrifblim(Level 32, Ghost/Flying)-Ominous Wind-Gust-Astonish-MinimizeGengar(Level 34, Ghost/Poison)-Shadow Claw-Poison Jab-Spite-Confuse RayMismagius(Level 36, Ghost)-Shadow Ball-Psybeam-Magical Leaf-Confuse Ray
To teach charizard shadow claw, you must get a heart scale and bring it to the move tutor. Once you do you get to teach it shadow claw.
Infernape can learn Shadow Claw by TM 65.
It's Pretty Good But i Prefer: Psychic, Poison Jab, Shadow Claw, Dark Pluse or Crunch.
After you beat fantina at the gym in hearthome city she will give you the TM shadow claw.
just train an nidoking and alakazam to level 50 here is what they should learnnidokingearth quakeice beamearth powerthunder (optional)alakazampsychichypnosisdream eaterthunder punchalso it might also help to give alakazam an lum berry and nidoking an quick claw
Tm 65 shadow claw is only available in Pokemon diamond/pearl ad patinum
Teach it TMs for all of them EXEPT sky uppercut is ONLY an egg move for riolu
The best poison type in diamond is definitely skuntank. Teach it the moves poison jab, toxic, shadow claw, and night slash. It'll be a great weapon in the elite 4. You can find a stunky (1st form) under the cycling road, in the grass.
you can get shadow claw on the goldenrod lottery on mondays as first price. and at route 42. hope this helps!
The Gym Leader's Pokemon are all ghost types: Drifblim lvl 32 (Ominous wind, gust, minimize, astonish) Gengar lvl 34 (Confuse ray, shadow claw, poison jab, spite) Mismagius lvl 36 (Confuse ray, psybeam, shadow ball, magical leaf)