LOL. Never knew that the Torque bow was so effective. Did it on Single player Casual no problems with just headshots from the sniper rifle!
I tried on Insane next and its just silly!! Going at it co-op from begining now so hopefully get it done before Gears 2.
Completed it on co-op Hardcore! He will get distracted by one of the players and you can then just pummel him with whatever you have!