@ohgodwhy: @DBZ_universe: yeah acnologias strong, and he would be able to kill mihawk for sure, but if mihawk acted fast enough, he could cut off his head before he does his roar or something else.
@eddz99: zeref does have the capability, although he lost to ultear so I dont think that its impossible for mihawk to slice him up first, but its more argueable
I agree with everything you just said...
He can slice Acnologia's head with his speed... because it takes a little time for Acnologia to charge the Roar and that's when he would be vulnerable.
I don't think Zeref would beat Mihawk... but When Ultear defeated him, he was not fully awake yet.. we haven't seen Zeref go all out.