Honestly, I can see it going to Shiki or Mihawk in a instant for anybody either Mihawk will one tap Shiki, or it will be the other way

I see it going to Mihawk.

The correct answer is probably Shiki, but since we don't really know the extent of his power, I will say Mihawk since there is a real chance of him being stronger

Mihawk, because Shiki has no feats

Mihawk though I could honestly see Shiki winning.

I think Mihawk since IMO he is on par with prime Roger