Out of all sixteen known Daedric Prince (I'm leaving out Jyggalag), who is the most powerful. And say if all of the Princes used Nirn as a battleground for their armies and maybe physical manifest themselves on, who would emerge victorious?

Most powerful would be Sheogorath but he is so unpredictable he coudl not win in a battle against the others due to his insaneness. So in the Battle Instant probably Molag Bal.