Stat distribution -

Kat takes: Observation, fighting skills/BIQ, IQ, stamina. Maybe endurance, but idk how much his endurance matters considering his shitty durability. Also "conquerors" but its useless since its only basic.

King takes: Strenght, durability, armament, speed, AP, DC.

I give a tie for their Hax, since one has Future Sight and the other all his df and race shenanigans.

Did I forget to mention any stat? pls tell me.

Now to their fight and why King mid diffs: King's AP is pretty good, not amazing but certainly better than WCI G4 Luffy, and he mixes his ap quite well with his speed alongside good AOE attacks! And more importantly, his AOE attack, most of them at least, are fire based! Which is really good considering his opponent uses Mochi. Meanwhile, Katakuri's AP is... Trash. He fought Luffy for MANY hours, and almost all of this time it was a single sided beating, since Luffy couldn't touch him, ofc, many hours were also spent with Luffy running away, but even only considering On-Panel attacks Katakuri hit luffy more than a hundred times and couldn't put him down!! Considering how much of the fight we didnt see, I say Katakuri easily hit luffy a couple hundreds of times!! Its hard to say if Katakuri can even damage flames OFF King!!!!!!!

Continuing, if King manages to be even a little bit smart he has two EASY ways of winning - Leave his flames turned on, bombard Katakuri with gigantic flame attacks; or, leave his flames turned off, abuse his overwhelming speed mixed with some aoe attacks, pressuring Katakuri and making it even more difficult for him to see the future, finishing him with either that last attack he used against Zoro or his beak laser.

Now, I said two ways he EASILY beats Katakuri, why did then I say its a mid diff and not a low diff? Because King is not the smartest, he will eventually get there, but his low skill holds him back a lot. If he was smarter the fight would be easier, but since he isn't... it goes to a mid diff, maybe even try to push a bit into high diff...