Can I get some Big Boss Tips?

Hello Everyone,
My friends and I decided to pick up Feng Shui for the first time in a long time for a new campaign. We primarily choose the system because of how it encourages imagination and Role-playing not only in the fights but in general. Now normally when I run I like to let the story dictate the outcome more then the rules, but I still like to work from a solid base, and that is where my problems have occurred.

I am running with a party of 8 characters and I wanted to have a big boss fight that would challenge the whole party. The first Boss I wrote up to take on the group alone was to weak. (He would have been a too much for any one of them individually but not even close for the group.) The next Boss was to tough and now only the most powerful attacks could hurt him and that left many of the characters ineffective.

Can I get some suggestions on how to write up a better big boss?

Thanks in advance!

I recommend

  1. It´s a very good fan made source book on par with professional publications.
  2. It has some useful tips and description for battles, NPC values and big boss battles.