Oden didn't have King of Hell (KoH). It is a style inquire to Zoro who created it.
What is KoH? KoH is a style where Zoro uses overwhelming amounts of CoA haki and combines it with ACoC haki or CoC haki coating.
The bottom right scene is an example of KoH.
The key to using KoH is having the power to flow and add overwhelming, enormous or extremely large amounts of CoA haki to a weapon. Smoke coming from a weapon is the result of overwhelming amounts of CoA haki added to a weapon. Whenever we see smoke coming from a weapon it's an indication overwhelming amounts of CoA haki is being used.
Zoro first use of enma showed us the results of overwhelming amounts of CoA haki added to a weapon (sword), smoke.
Enma forced Zoro to release an enormous amount of CoA haki. It was so much haki his arm shriveled up. The result of all of that CoA haki being added to the sword was smoke coming from enma.
Smoke coming from a sword because of overwhelming amounts of CoA haki has been consistent throughout Wano. Every single time Zoro lost control of enma and it forced him to release overwhelming amounts of CoA haki we see smoke coming from the sword.
Zoro can freely add overwhelming amounts of CoA haki to any sword and without needing to use ACoC at the same time. As seen in the top right scene.
Neither overwhelming amounts of CoA haki nor KoH is needed to control enma, just large amounts of CoA haki. That why Zoro didn't lose control of enma when he wasn't using KoH or overwhelming amounts of CoA haki while fighting King.
And again post Wano.
That explains to us why Zoro only used KoH when he was going on the offense and attacking King. Not when he was just clashing or blocking King attacks.
There's the proof KoH is not needed to control enma. Anyone claiming Zoro needs KoH to control enma is pushing headcannon.
Oden never had KoH, a variation of KoH or used overwhelming amounts CoA haki. That can be determined by the lack of smoke coming from his swords. Anybody claiming anything different is pushing headcannon.
Here's the proof.
No smoke.
I don't know why some focus on this scene.
All it tells us is 8 year old Oden could use enma with no haki. It doesn't mean Oden had mastered enma by the time he was 8. We saw the same thing from Zoro when he us6e enma early in the war with no haki.
This is before he mastered enma.
Anyone claiming the reason we don't see smoke coming from Oden's swords is because he surpassed the smoke state and it disappeared or some other BSis full of it. I've already proven overwhelming amounts of CoA haki causes smoke to release from a sword.
The more CoA haki added, the more smoke is releases from the sword.
Here manga proof.
Zoro using overwhelming amounts of CoA haki with his sword.
Notice the amount of smoke coming from each sword.
Now notice the amount of smoke coming from a sword when much haki is added.
There's more smoke coming from the sword.
I shouldn't even need to explain this since there's absolutely no evidence supporting using more CoA haki than the amount Zoro used makes the smoke disappear.
This scene is just Zoro questioning how Oden could use some much CoA haki while easily controlling enma. Zoro wondering how much CoA haki he should use to control enma. Finally realizing large amounts of CoA haki is the key to fully controlling enma. Instead of just using large amounts of CoA haki, Zoro releases all of his haki, CoA and CoC.