Nidoking would be the superior wallbreaker since it has Megahorn to skewer Mew, Cresselia, and Umbreon something fierce. On the other hand, Nidoqueen is not that far behind in terms of wallbreaking prowess, and her better (and usable) bulk allows her to consider her support options, such as Toxic Spikes, Stealth Rock, and Roar, or even permit an item other than Life Orb, such as Black Sludge. Since Queen can focus on her bulk, she can claim to actually switch into shit like Mienshao, Heracross, Escavalier, Mega Aggron, Mega Ampharos...while Nidoking can only really switch into...I dunno? Florges? I don't see much reason Queen shouldn't be right next to King in A Rank.
Metagross, on the other hand, is a trickier case. It is meant to be built like a tank, but it can falter against a good majority of Pokemon in the tier. Hydra breaks it, Mega Houndoom / Absol / Blastoise breaks it, Victini / Darmanitan breaks it, Nidos break it, Honchkrow breaks it, the reintroduced Crawdaunt breaks it...and then Metagross doesn't do a spectacular job wallbreaking either, since Forretress, Hippo, Swampert, Will-O-Wisp Mew, Umbreon, Vaporeon, and Suicune wall/beat the shit out of it. Metagross had better have some outstanding stuff in its movepool to warrant such a high rank.
- Steel STAB: It's no longer even the strongest Steel-type move in the tier, since 0 Atk Mega Aggron's Heavy Slam totally hits harder against a good majority of opponents. At this point you're probably going out of your way to try to make Meteor Mash top that Heavy Slam, like hoping for Attack boosts or slapping a Choice Band on it. Too bad the former can get forced out too easily for that rare chance to come into play, and locking oneself into a Steel-type move when stuff like Suicune, Raikou, Mega Blastoise, Victini, etc. lurk in this meta is asking for trouble.
- Psychic STAB: Yeah that's cute, hitting the likes of Chesnaught and Heracross for more damage. How are those weaknesses working out for you?
- It has Stealth Rock, which isn't new even on a tank like Metagross, since other tanks such as Swampert, Hippowdon, and of course Mega Aggron boast their own share of offensive presence. This also means you cannot use Assault Vest with it.
- It has Pursuit, but there are so few targets Metagross would want to use this on: Ghosts won't flee from Meta due to their newfound advantage, and most Psychics (Mew, Victini, Slowbro, Cresselia) won't bother with Meta's Pursuit either.
- Bullet Punch is admittedly nifty, since it nails Pokes such as Mega Dactyl and Kyurem. However, it doesn't really hit much else, and doesn't even outspeed the most relevant Sucker Punch user in the tier (Honchkrow) to be able to avoid it.
- Ability to go mixed: a usable Special Attack stat with Grass Knot and HP Fire can lure out some hard checks/counters such as Swampert and Forry and proceed to beat them, but they don't hit enough threats to be very useful, as Vappy/Suicune shrug off Grass Knot while HP Fire barely grazes Mega Aggron.
- Agility is probably the big selling point about Metagross as far as I can tell, but is this really enough to warrant A Rank?
- Explosion is probably also one of Meta's true selling points imo, blowing itself the hell up to weaken a foe.
I won't voice out my Rank on Metagross yet, I just want to know if these advantages merit its high placing.