Overwhelm

Heavy Weapons Specialist: 15th level When you use your Second Wind while wielding a weapon with the heavy or strength properties, if you hit with the first attack roll you make, or if one creatures fails the saving throw against your weapon's burst or rapid property, before the end of your next turn, you treat the hit as a critical hit. If you miss with the first attack roll you make before the end of your next turn, or one target succeeds on the saving throw against your weapon's burst or rapid property, you instead deal normal weapon damage.

Granted by Heavy Weapons Specialist at 15th level.