Even though I wouldn't disagree if King happened to be > Marco and Katakuri, but it is very well debatable how to rank these 3.
No, it's really not.
Some of King's feats in the little I've seen so far:
- Defence and durability
- He's "on another level" entirely from Kaido.
- He no sold Tatsumaki.
- Same Tatsumaki cut up Kaido and had him coughing up blood for several panels.
- He no sold Shishi Sonson.
- Zoro's go to technique for overcoming hard defences (see Daz Bones, Kaku and Bartholomew Kuma).
- Offence
- He overpowered Zoro's Ul Tora Gari.
- He overpowered Zoro's block.
- The same Zoro was able to momentarily hold back Hakai.
- Zoro could not block or defend against his air slashes.
- Zoro easily deflected Kaido's Wind Scythes.
- Mobility
- Easily dodged Zoro's Pound Cannon.
I may be missing some feats (I haven't been following the chapters).
King's defence is far above whatever Marco or Katakuri can hope to dish out (none of them have attacks of the calibre of Tatsumaki, let alone Shishi Sonson).
King's offence is also at a level that they would face difficulty withstanding for extended periods of time.
And his mobility also gives him an extra edge.
Regeneration and Future Sight would let them hang against him for a decent while, but he'll win both fights with barely any HP damage and only some stamina lost.
Let alone Awakening/Haoshoku, neither Kata nor Marco can defeat King with the little he's shown so far.
This shouldn't be a surprise; Rooftop Zoro was stronger than Katakuri/Marco (at worst, you could have made the case that he was comparable to Marco, but I find even that a hard sell), and King is himself significantly stronger than Rooftop Zoro.
Before unlocking Haoshoku coating, Luffy would have lost badly to King as well.