Can anyone gimme an absolute counter to most of mag sets pls ts is so annoying
For the Stored Power / setup varaints sets, best counter by far is Encore Specially Defensive Magearna, which can encore the enemy Magearna into a setup move & freely Pivot into a Ground-type to start threatening big damage. Roar Heatran and Volcanion are also both quite effective vs setup variants with Roar (or Haze in Volcanion's case) but need to watch out for various coverage like Focus Blast or Thunderbolt (and Volt Switch). These two can be chipped down by defensive sets long-term with Volt Switch, but this is no different than your usual interactions between Clefable and Heatran for example (where Clefable Knock's Heatran / Excadrill off and chips it long-term with Hazards). Specially Defensive Excadrill is excellent against defensive sets and does quite well vs set-up variants as well, though needs to watch out for the odd Focus Blast. Running SD is also ideal just to deal with the odd ID variant as well. Against more passive variants of the setup sets, various phazers like Talonflame, Skarmory, and Swampert will all work as checks, but can take heavy damage for certain coverage moves like Fleur Cannon or Thunderbolt if the Magearna is a more fast pased offensive CM variant.
Setup / defensive magearna variants can be lured in and crippled by various Scarf Pokemon such as Darkrai, Gholdengo, and Latios - which is a more one time measure, but can still work well enough in faster games if you can keep th,e spikes pressure up. I gave a few other counterplay options, like Black Sludge + Trick Slowking-Galar + Sand Tomb SD Scizor a shot as well and these performed pretty well against Mag - while also not being entirely useless vs various other MUs, but also had some notable trade-offs. In Slowking-G's case, being pursuit weak just sucks, while Scizor could struggle in a few MUs without Knock such as against Rotom-W and Corviknight. There are a lot of Pokemon I haven't been using, but I think should do fine vs Mag in general like Hippowdon, certain Gholdengo variants, certain variants of miscellaneous mons like Crobat (haven't built this since I'm unsure what it should run), and big damage dealers like Mega Zard-Y, Blaziken, Mega Zard X, Mega Emboar, Ceruledge, Armarouge, and a few others that can make it annoying for it to execute its gameplan.