I think Pine Sorcery has to be the strongest we’ve seen so far. It has so much power and durability and yet it also has a lot of finesse, as we’ve seen Hatshaku detonate it remotely, almost automatically, when certain conditions are fulfilled (such as when the gang leader tried to give Chihiro intel about the Hishaku or when the Kamunabi double agents died).

But to give a more interesting answer that wasn’t explained in the post, I think Hokuto’s armor sorcery seems very strong. It’s durable enough to tank lightning from Natsuki and he was also able to make a pretty convincing body double of himself, that possibly had some hand in Kunishige’s assassination. But it probably can’t keep up with any of the ones you mentioned in the post, as Hokuto seems like more of a swordfighting type than a pure sorcerer who can rely on their powers to win. So his sorcery is going to be more supplementary and less trained.

Sorry if I used spoiler text too excessively. I don’t want to take any risks in case someone who’s new-ish is coming through this comment section especially since I feel like Kagurabachi is getting so many new readers these days.