You are able to bull rush an opponent straight to the ground.
Prerequisites: Improved Bull Rush, Merciless Rush, worshiper of an evil god.
Benefit: Whenever you make a bull rush attack and your check exceeds the target’s CMD by 5 or more, you can choose to expend one of the increments of 5 feet you would normally move the target back to instead attempt to trip the target as a part of your bull rush action. This does not provoke an attack of opportunity.
Pathfinder Player Companion: Faiths of Corruption © 2011, Paizo Publishing, LLC; Author: Colin McComb.