Heretical Behavior is an origin trait in Destiny 2 that can appear on 4 weapons. An enhanced version exists on crafted and some newer weapons.
What Heretical Behavior does
Sustained weapon damage or final blows versus powerful targets grant this weapon bonus reload, handling, and damage versus combatants. Gain this bonus immediately for a longer duration when you are revived.
Enhanced version
Sustained weapon damage or final blows versus powerful targets grant this weapon bonus reload, handling, and damage versus combatants for an improved duration. Gain this bonus immediately for a significantly longer duration when you are revived.