( HoW AR9104 ) Emmerich Hawk just disappears maybe in 2 seconds after he turns hostile.
The way I find viable includes:
1. Feeblemind : He will stay put until you cut him down . Reloads are required, and reputation will drop.
2. Finger of Death : He will die instantly. Reloads are required, and reputation will drop.
3. Shapechange + Improved Haste + Timestop : He will die a mindless death. No reload required, no reputation drop.
4. Feeblemind + Protection from Evil 10' Radius + Cacofiend / Summon Fiend/ Gate : He will be slained by demons. Reloads are required, no reputation drop.
Edit 1: Sorry I just figure out I can lower the difficulty to normal. Then no spells are required and I can cut him down in 2 seconds. Yet I am still wondering if there are other ways to kill without losing reputation.