Power Attack

Heroic Tier
Prerequisite: Str 15
Benefit: When making a melee attack, you can take a -2 penalty to the attack roll. If the attack hits, you gain a +2 bonus to the damage roll (or a +3 bonus to the damage roll with a two-handed weapon).
    This extra damage increases by level, as shown on the table below, but the attack penalty remains the same.

Published in Player's Handbook, page(s) 199.