You can bull rush an opponent straight to the ground.

Prerequisite(s): Improved Bull Rush, Merciless Rush, worshiper of an evil deity.

Benefit(s): Whenever you make a bull rush attack and your combat maneuver check exceeds the target's CMD by 5 or more, you can attempt to trip the target as part of your bull rush as a free action. This does not provoke an attack of opportunity.

Combat Trick

Source PPC:WMH

Note If using the optional Stamina Pool rules, the following trick may be used with this feat.

Combat Trick: After succeeding at a bull rush combat maneuver check, you can spend 4 stamina points to attempt to trip the target with Squash Flat regardless of your bull rush combat maneuver check's result.