Depends on individual ambition since Enma scales to each user differently.
Enma was satisfied even with child Oden's level of haki that never used aCoC.
Enma was satisfied with rooftop Zoro's level of CoA.
Once his kingly ambitions showed up, Enma was satisfied only by largest amounts of haki ever released.
Imo the reason Enma was fine with kid Oden is because it was made for Oden. The sword grew as Oden did and eventually, it got used to the incredibly high levels of Haki Oden was supplying it.
So when anyone else picks it up it forces that level of Haki out of them, but obviously only top-tiers can sustain that level of Haki being constantly outputted. Zoro was initially able to force his Haki back and restrict its flow into Enma thanks to his level of Haki control. Personally, I believe that Enma saw potential in Zoro and was also calmed by the fact that Zoro wielded Wado Ichimonji.
So on RT, up against two Yonko, if Enma acted up Zoro would've died for sure. Enma doesn't wanna kill Zoro, it wants to test him and so it allowed Zoro to regulate it because even Oden couldn't have beaten these two together. Zoro's kingly ambitions have always been the same since chapter 3; he wants to become the greatest swordsman under the heavens.
He went all-out and his CoC seeped out in Asura. His CoC comes out when he holds absolutely nothing back which is not often in the manga - usually his fights don't go to extreme-diff. It certainly hadn't happened post-TS until this point and so this was the first time his CoC was stated to seep out on panel. Although he may have unconsciously used it against Kaku and Monet.
Now we move onto King. Zoro was struggling with a mere YC1 - this is a pathetic performance unworthy of anyone who dare call themselves Enma's owner. So Enma tested Zoro because if he fails here then he doesn't deserve it. Zoro passed the test and can now output Oden levels of Haki in KOH, at least that's how I see it.
@OP: Anyone can hold Enma and get their Haki sucked out casually. Anyone with good Ryou control can hold Enma and restrict their Haki flow so it doesn't get sucked out casually. Only Oden-level characters can appease Enma permanently.