The first one of those is Tailwind. I got reqs easily with Tailwind because of how strong Celesteela + Tailwind is. There are also other mons that are really good in Tailwind like Nihilego and Tapu Lele, but Celesteela stands out because of it's natural bulk. There aren't many ways to beat Tailwind teams, the only bad matchups that Tailwind has are TR and other Tailwind teams. It's is also much more broken if paired with Aurora Veil, because it lets Celesteela get an Autotomize off, which is most of the enough to win. Tailwind is generally unhealthy and uncompetitive for the metagame and I would say that it's really similar to Baton Pass in OU before it was banned.
If anything tailwind gives us some sort of check to those agility sweepers, seriously without it how do u even revenge mons like landorus celesteela or lopunny? They hit way too hard and, just like tailwind, they outspeed everything.
The only difference is they keep their boosts until they switch out, basically after u set up a rock polish or agility you just stay in and sweep cause youre not forced to switch out after 3 turns. Idk about u but agility spam sounds just as bad as tailwind spam