Yeah, right-clicking on an enemy would bring up your power menu and right-clicking on a power in that list would give you the option to underpower (less power; less damage), overpower (more power; more damage), or super overpower (a lot more power; a lot more damage) your attacks.
Unfortunately, Irrational Games, in their infinite wisdom, decided to do away with FF's energy system, so now you can only overpower your attack.
You can still right-click and bring up your attack list, but holding Ctrl is what overpowers your attack. You might be able to right-click on your power, but I haven't used that functionality in forever.