Is there any way that monsters/eidolons can qualify for the 1 1/2 times power attack bonus with their primary attack?
Power Attack (Combat): "This bonus to damage is increased by half (+50%) if you are making an attack with a two-handed weapon, a one handed weapon using two hands, or a primary natural weapon that adds 1-1/2 times your Strength modifier on damage rolls."
Natural Attacks: "If a creature has only one natural attack, it is always made using the creature's full base attack bonus and adds 1-1/2 the creature's Strength bonus on damage rolls. This increase does not apply if the creature has multiple attacks but only takes one."
A biped eidolon that spends an evolution point to replace its claws with a slam would qualify for 1.5xStr and the +3 PA bonus.