I don’t see him having any form of CoC. Him crying like a bitch begging for his life at Marineford isn’t the quality of a king.
1- He multiple times showed that he does crazy things that most people are scared to do; such as killing WB's son Thatch (he knew that WB would avenge his son), throwing off his Shichibukai title in front of the Marines and infiltrated Impel Down before that, tried to eat a second DF despite the risk of dying etc etc. He showed the will to dominate and conquer. He was clearly trying to deceive WB again due to ''acting like his son'' before, but WB didn't fall for BB's trick twice, still BB's will was strong enough to resist WB's attack, he then shoot WB to death, and killed him.
2- Oda also doesn't care about that, they never said people can have CoC based on that. It's related to overpowering the opponent's will. An Emperor clearly has that, if even the underlings of an Emperor has it. (Such as Oden, Ace, Katakuri, Rayleigh etc etc)
Here, these are some CoC users;