Nidoqueen is a very difficult Pokemon to deal with for slower teams, due to how perfectly placed its attributes are for utterly demolishing slower RU teams. First of all, Nidoqueen, while slow by offensive team standards, really has a perfect speed tier; with its Speed, it outspeeds virtually every strong wall in RU, and due to its obscene coverage, it is able to 2HKO most of RU's walls and even OHKO some of them. The fact that Nidoqueen cannot be dealt with by traditional defensive methods such as Toxic poison and Thunder Wave also means that Nidoqueen puts defensive teams at a significant disadvantage, as the defensive team must outplay the Nidoqueen user numerous times in order to take it down, while not losing multiple Pokemon in the process. Because of this, slower / balanced teams have to be incredibly offensive in order to stop Nidoqueen from coming in freely, as otherwise, it will almost always get a kill, if not more. Yes, there are some answers to Nidoqueen for slower teams, such Uxie, Gardevoir, Clefable, and such, but even then, if Nidoqueen REALLY wanted, it could just use Shadow Ball / Focus Blast to 2HKO them; the thing is, no one has needed to do this because no one uses slower teams with these defensive answers to Nidoqueen anymore, simply because it can already overwhelm them with its regular set, which speaks a lot about how strong Nidoqueen is.
Essentially, Nidoqueen, by absolutely demolishing slower teams single-handedly, centralizes the metagame around fast, offensive sweepers who are able to outspeed Nidoqueen, for they are the best bet against Nidoqueen. No other Pokemon does this to the extent Nidoqueen does, so therefore, I feel that Nidoqueen should be banned.