Once per battle, make a fighter melee attack as a free action after one of your melee attacks drops an enemy to 0 hp.

Adventurer Feat: 

If you have your move action available, you can use it before making your Cleave attack to reach an enemy you are not already engaged with.

Champion Feat: 

You can use Cleave twice each battle, but only once a round.

Epic Feat: 

You gain a +4 attack bonus with your Cleave attacks.