Esdeath's not getting one-shot by Kamui. First of all Kakashi won't use it in the beginning of a fight against someone he has no knowledge of. And Second, I doubt he'd get a clean look at her. Judging from her fight with Akame, they're probably gonna be moving around a lot. Why shouldn't Esdeath be able to react to Kakashi? All she has to do is use Makahadoma and it's a guaranteed win. Naruto characters have been killed by Kunai before so an ice dagger should work just fine.