Possible Duplicate:
What determines when you do a finishing move?
Is there any way I can guarantee that my next Killing Blow will trigger a Finishing Move Scene?
I am making a Skyrim Video and the new Bow Finishing Move scene does not proc that much.
set killmoverandom to 100should allow you to increase the chance of triggering finishing moves". Also, I wrote a more detailed answer to your question here. – galacticninja Nov 20 '13 at 11:27