I'm pretty sure Kaido's Thunder Bagua is imbued with Conqueror's Haki. I've always had a feeling that it was possible to do so way back during Fishman Island with Luffy vs Hordy, and Luffy used "Snakeshot."
On paper it seems like such a low level attack, but as you can see it dealt considerable amount of pain to Hordy. Some people use to argue that it was just CoA along the same vain that Rayleigh used, but now as we can see that Luffy wasn't capable of using that kind of CoA until just recently. Others argued that it was just Luffy's grip strength, but that doesn't make much sense either as Luffy used it underwater where his overall strength would be considerably weaker. So it shouldn't be able to cause that much pain to someone who is durable enough that took an Elephant Gatling to be taken out. So I am now even more so convinced that CoC can be imbued into attacks.