Galarian Slowking to B+
Checks important special attackers (most notably Cm Clef) and unlike Pex, Ferro, and Tran it isn't weak to any of clef's common coverage options. It is also pretty hard to switch into with its great movepool and STAB options which make Sludge Bomb hard to beat. It partners up very well with Ash-Greninja most notably, as it can threaten out Agren's checks like Spd Tapu Bulu, Tapu Fini, Ferrothorn, Clefable, and makes sure Toxapex will not be able to switch into Ashgren after Future Sight, while Greninja can destroy most of Glowking's bad MUs and can abuse Future Sight as much as possible with U-turn or use Spikes to make Slowking's Sludge Bomb and Flamethrower even harder to switch into. Some other solid teammates are Mega Lopunny and Dragon types which appreciate Glowking's ability to check Cm Fini and Cm Clef. Future Sight + Regenerator is just very good.
Now despite this it has several drawbacks which prevent it from being A-. It has its fair share of bad top tier MUs, and its lack of even passive recovery is expoitable. It is also rather reliant on AV to check things reliably which gives it a slightly harder time against Knock Off which its checks sometimes carry.
I agree with nomming Ash-Greninja and Kart to at the very least S. I think Blaziken should be in C, B+ seems ridiculous but I don't think it should be Unranked. I also think Volcanion deserves a bigger rise, probably to B-.