Attack of Opportunity
Level 6 champion Barbarian

Trigger: A creature within your reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it’s using.

You lash out at a foe that leaves an opening. Make a melee Strike against the triggering creature. If your attack is a critical hit and the trigger was a manipulate action, you disrupt that action. This Strike doesn’t count toward your multiple attack penalty, and your multiple attack penalty doesn’t apply to this Strike.

Cleave
Level 6 Barbarian Rage

Trigger: Your melee Strike kills a creature or knocks it unconscious, and another foe is adjacent to that creature.

You swing clear through one foe and into another. Make a melee Strike against the second foe.

Attack of Opportunity
Level 6 Champion

Trigger: A creature within your reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it’s using.

You lash out at a foe that leaves an opening. Make a melee Strike against the triggering creature. If your attack is a critical hit and the trigger was a manipulate action, you disrupt that action. This Strike doesn’t count toward your multiple attack penalty, and your multiple attack penalty doesn’t apply to this Strike.

Storm Retribution
Level 6 Druid

Prerequisites: storm order, tempest surge, order spell

Trigger: An opponent adjacent to you critically hits you with a melee weapon or melee unarmed attack.

You lash out, directing a burst of storming fury toward a creature that has harmed you. You cast tempest surge on the triggering opponent and push that creature, moving it 5 feet away from you if it fails its Reflex save, or 10 feet if it critically fails. This movement is forced movement.

Guardian's deflection
Level 6 Fighter

Trigger: An ally within your melee reach is hit by an attack, you can see the attacker, and the ally gaining a +2 circumstance bonus to AC would turn the critical hit into a hit or the hit into a miss.

You use your weapon to deflect the attack against your ally, granting a +2 circumstance bonus to their Armor Class against the triggering attack. This turns the triggering critical hit into a hit, or the triggering hit into a miss.

Crane Flutter
Level 6 Monk

Prerequisites: Crane Stance

Trigger: You are targeted with a melee attack by an attacker you can see.

You interpose your arm between yourself and your opponent. Your circumstance bonus to AC from Crane Stance increases to +3 against the triggering attack. If the attack misses you, you can immediately make a crane wing Strike against the attacker at a –2 penalty, even if the attacker isn’t within your reach.