i've been watching forums for some time but never really felt the need to post, since i always agreed with the tiers in pretty much all generations, someone did an excellent job all those years
i only have my point of view that of someone who mostly plays aggressive teams and in my opinion Pheromosa is ridiculous:
she can be used as revenge killer and sweeper with minimal opportunity cost, yes she's very fragile and has a few counters but other than that she destroys anything, Beast Boost is a crazy ability, if she kills something, anything she spirals out of control and is able to kill even walls, especially paired with support and some pokemons that counter her counters in my opinion she's unstoppable
even if she's just coming in after KO's to U-turn she's going to do tons of damage, while against other non-bulky sweepers she seems able to one hit KO with unresisted stabs
essentially she's a wallbreaker that can also kill most sweepers out there, even if only a couple of pokemons in your team are soft to her you're going to have some serious trouble
she's supposed to be countered by priority moves but there's also Tapu Lele which is a great pokemon to play even without the obvious synergy with Pheromosa
overall i think that her offensive power is simply too good for the OU meta and therefore i believe that she should be banned