Lethal Strike (RoF Feat)
From D&D Wiki
 Lethal Strike [Heroic]
You strike with pinpoint precision and accuracy, taking advantage of angles and location to deal extra damage.
Only available if your first class level is from a Hero class; limit one Heroic feat per character.
When you successfully confirm a critical hit, you deal an additional +1d4 damage against your target. At level 5, and every five levels after (10, 15, 20), this damage is increased by an additional 1d4, to a maximum of +5d4 at level 20. If the enemy is a Dragon, all dice are increased to d6s.