Unstoppable

Effect: 

Once per battle, declare you're using Unstoppable before making a barbarian melee attack. If your attack hits at least one target, you can heal using a recovery.

Adventurer Feat: 

The Unstoppable recovery is free.

Champion Feat: 

Add double your Constitution modifier to the healing the recovery provides.

Epic Feat: 

You can use Unstoppable twice per battle.