Earning this trophy will have you perform the killing blow on any enemy with a special ability a whopping 500 times. A special ability is an ability that can be mapped to one of your quick UI slots (accessed by holding down L2 then pressing the corresponding Face button). The game automatically gives everyone a point in the Storm Bolt ability during the tutorial of the game so those not wanting to commit to other abilities can simply spam this one.
Remember that it doesn't matter how you injure enemies, as long as the killing blow is from an ability you're good to go. Also note that sustained abilities do not count towards this trophy.
While this will take quite a bit of time to achieve, it can be made easier by returning to lower level areas after your character is stronger, this way abilities will one hit kill enemies and you can grind it out pretty quick. This trophy features the same type of challenge as the "Shock and Awe" trophy.