I would like Busoshoku Haki Emission and Haoshoku Haki Redgrave D. Zelgadis.
Zelgadis is a natural born conqueror, everything about his character exemplifies this. From his laugh "seihai" meaning to conquer, to even the power of his Devil Fruit which grants the ability to generate the Purgatory Flames of Conquest and Domination.
His ambition to become Pirate King is rooted in the belief that in doing so he will invite even greater challenges to overcome.
His character is not like other Conquerors, where their merit is based on what territories they acquired, the organizations they built, it has nothing to do with running a kingdom or anything large like that. To him, the act of Conquest is deeply personal tied to one overcoming their own weaknesses, and inner demons.
What he does, and indeed what is apart of his backstory as the Ghost of Paradise is to help others conquer those selfsame fears. He elevates others to become their own masters, which is demonstrated in his personality. Yes he is endlessly arrogant, erudite, and mischievous. While his Devil Fruit would easily allow him to bewitch others for longterm personal gain, he actually tempers that impulse, because his pride as a conqueror demands that he do so without the use of such a crutch. It would cheapen the victory in his eyes.
In his current fight with Commodore Dave, he expresses joy and pride in both Dave and the Marines as they struggle to overcome the challenges in front of them. Even if that challenge is himself. His desire to see others rise to try and overcome the obstacles in front of them doesn't stop, even of their an enemy.
That is why Zelgadis should have Haoshoku Haki.
For Emission and general Haki strength I believe he would possesses extraordinary awareness and skill with Haki. One of the primary reasons is his Devil Fruit which actually requires that exert his will, to enact its effect. The devil merely acting as an extension of his already impressive willpower, but the fact that it is as draining as using Haki. As a result he was aware of the power of his will long before he had ever learned of Haki. As a result of this, and his constant need to challenge himself against difficult odds he has put himself into the grinder to manifest and expand his strength in Haki.