Borderlands 2: No Kill Like Overkill
Spent 25 or more skill points total on lower tiered skills in the Gunlust tree.
 Level Requirement
When you kill an enemy, the excess damage you dealt is added to the damage of your next shot.
"I'm looking for a really big gun that holds a lot of bullets"
 Number of Ranks
When you kill an enemy, you gain a bonus to gun damage equal to the amount of excess damage you dealt to the enemy you just killed.
Percentage of Overkill Damage converted into Damage on your next shot: 100%