By Law’s word we know that :
Dofla’s Haki > Cracker’s
Dofla’s Haki was strong enough to allow him to free himself from Kuzan’s ice.
I guess Kaido could brush off Gamma knife thanks to his haki. That we know his stronger than Doffy’s.
Now we can make direct Haki comparison between character.
For example : Zoro’s Haki > Law because Zoro could freed himself from Fujitora’s gravity with Haki alone while Law’s need his DF to do so.