Takedowns with weapons that have a damage type matching your subclass element grant you Super energy. While your Super energy is full, you instead gain a temporary bonus to weapon damage of the type matching your subclass element.
Final blows or sustained damage with weapons matching your equipped Super damage type grant you Super energy. When your Super energy is full, you instead gain a temporary bonus to weapon damage of that type. When you've exhausted your Super, matching elemental weapons' damage temporarily causes explosions around the target.