Platinum Games posted a blog on their official site regarding the development of Metal Gear Rising Revengeance. In this specific post character animator Hirokazu Takeuchi explains how the concept of free cutting translated to working on different enemy reactions. For every specific part of an enemy that the player could choose to slice off, the studio had to create another animation. Takeuchi also added some videos that demonstrate just a few of the ways enemies can react to your actions.
To read the full post, go here.
Source: Platinum Games