I think that Mihawk is an expert user of the Kenbonshoku Haki.
- His ability, not coming from a devil fruit, can be helped by that type of Haki.
- He said that become the best swordsman needed a lot of exercises: Rayleigh said that training Haki needs years.
- He seems not to be able to use Busoshoku Haki, as noticed when he didn't slashed Jozu at the beginning of the WB war.
- At the opposite, a lot of people (in real world) are sure that he must be a Haki user.
What do you think?