In order to get this, you need to create 100 power explosions on enemies.
To do this, you need to have selected both a Primer and a Detonator from your skill tree. The Primer will have a symbol in the top left of the icon and will also tell you in the description that it is a Priming power. The Detonator will have a symbol in the upper right of the icon that looks like an explosion, and will also tell you in the description that it is a Detonator.
Personally, I've been using Incinerate to Prime and Overload to Detonate. You need to make sure that you do them in order. Primer (Incinerate or other Primer) and then Detonater (Overload or other Detonator). Doing this in order on an enemy will cause a huge explosion.
Do this 100 times to unlock the trophy.