While the lower ranks are being tidied, I'd like to suggest Nidoqueen to D
Nidoqueen's supposed niche over Nidoking is it's added bulk at the cost of a little power, which seems like a reasonable quality to focus on as an offensive hazard setter. However, Nidoking is a niche enough hazard setter as it is and his main pro is that a lot of defoggers and spinners can't switch in on his coverage and decent power when boosted by LO and Sheer Force; he himself is also able to switch in on a lot of more passive defoggers for that reason, although he is himself forced out by a lot of offensive defoggers or spinners (Starmie, Latis and Excadrill being the main ones). Nidoqueen is still beaten or at least heavily pressured by all of the same mons, and although her better bulk can, with a defensive set, save her from a couple of 1HKOs or 2HKOs, in order to do that she has to sacrifice the ability to pressure those mons in return, effectively allowing them all to switch in for free. There are just so many better defensive entry hazard setters available in OU, toxic spikes and Sheer Force boosted attacks (which are still pretty weak) being her only relevant niche over most of them. The main reason to pick Nidoqueen as a defensive hazard setter is that she can soft check Mega Manectric while healthy. Even then, Tentacruel and Scollipede are usually (depending on the situation and team) better setters of Toxic Spikes, and with Protect+EQ included Scollipede can check Mega Manectric too in some situations.
EDIT: all that said about Nidoqueen as a bulky toxic spiker with some offensive presence, I've also realised that Dragalge exists too.
Naturally as an offensive hazard setter she's just entirely outclassed by Nidoking.
Her relative weakness compared to Nidoking is sort of already reflected but tbh I think her tiny and extremely team-specific niches are more at home in D rank.
Similar note, what is Froslass doing? Sure, nothing else has her combination of Spikes, Destiny Bond and Ghost typing, particularly with her speed tier, but those could be listed as reasons to try to use it in any tier... doesn't mean it's actually viable - what specifically does it achieve that can actually yield results in OU to make it any more viable than the average D rank mon...? Could anyone shed some light on this, please? I'm sure I'm missing something. If not, I'll nom that to D too. As an offensive hazard setter, it's successfully pressured by enough common threats including most priority users and all relevant magic bouncers while it's just too weak to offensively pressure anything in return; resultantly, using it in OU can in all but the most select of situations end up just making one's own life more difficult for oneself, when there are just better offensive Spikes users around. It's not a terrible mon, but as a hazard setter it's no better or worse than Roserade which is just functionally different (and also has much better offensive presence and more valuable utility), and also resides in D rank. The main issue with Froslass as a hazard setter is that it only really fits on certain hazard stacking HO variants as a Sash lead, which is a niche in itself, and the existence of better offensive spikers like Scolipede means that any higher than D is really overselling how relevant Froslass really is to the metagame.
Nidoqueen's supposed niche over Nidoking is it's added bulk at the cost of a little power, which seems like a reasonable quality to focus on as an offensive hazard setter. However, Nidoking is a niche enough hazard setter as it is and his main pro is that a lot of defoggers and spinners can't switch in on his coverage and decent power when boosted by LO and Sheer Force; he himself is also able to switch in on a lot of more passive defoggers for that reason, although he is himself forced out by a lot of offensive defoggers or spinners (Starmie, Latis and Excadrill being the main ones). Nidoqueen is still beaten or at least heavily pressured by all of the same mons, and although her better bulk can, with a defensive set, save her from a couple of 1HKOs or 2HKOs, in order to do that she has to sacrifice the ability to pressure those mons in return, effectively allowing them all to switch in for free. There are just so many better defensive entry hazard setters available in OU, toxic spikes and Sheer Force boosted attacks (which are still pretty weak) being her only relevant niche over most of them. The main reason to pick Nidoqueen as a defensive hazard setter is that she can soft check Mega Manectric while healthy. Even then, Tentacruel and Scollipede are usually (depending on the situation and team) better setters of Toxic Spikes, and with Protect+EQ included Scollipede can check Mega Manectric too in some situations.
EDIT: all that said about Nidoqueen as a bulky toxic spiker with some offensive presence, I've also realised that Dragalge exists too.
Naturally as an offensive hazard setter she's just entirely outclassed by Nidoking.
Her relative weakness compared to Nidoking is sort of already reflected but tbh I think her tiny and extremely team-specific niches are more at home in D rank.
Similar note, what is Froslass doing? Sure, nothing else has her combination of Spikes, Destiny Bond and Ghost typing, particularly with her speed tier, but those could be listed as reasons to try to use it in any tier... doesn't mean it's actually viable - what specifically does it achieve that can actually yield results in OU to make it any more viable than the average D rank mon...? Could anyone shed some light on this, please? I'm sure I'm missing something. If not, I'll nom that to D too. As an offensive hazard setter, it's successfully pressured by enough common threats including most priority users and all relevant magic bouncers while it's just too weak to offensively pressure anything in return; resultantly, using it in OU can in all but the most select of situations end up just making one's own life more difficult for oneself, when there are just better offensive Spikes users around. It's not a terrible mon, but as a hazard setter it's no better or worse than Roserade which is just functionally different (and also has much better offensive presence and more valuable utility), and also resides in D rank. The main issue with Froslass as a hazard setter is that it only really fits on certain hazard stacking HO variants as a Sash lead, which is a niche in itself, and the existence of better offensive spikers like Scolipede means that any higher than D is really overselling how relevant Froslass really is to the metagame.