Through the power of chaos and absolutely unpredictable and ingenius tactics, of course.
E: and it goes without saying but: More explosives and seals than you can shake a stick at.
That's a given. Chaos, unpredictability, and tactical genius are the only things Hazou can do.
Give me specifics, not rhetorics. If you were writing an action plan to defeat Kei what would be in that plan?