The antonyms for the word "most case hardened" are soft, pliable, flexible, tender, and malleable. These terms refer to the absence of the harshness and rigidity that are associated with case hardening. In particular, they denote materials or substances that are relatively easy to shape or reshape without breaking or cracking. A soft metal, for example, is one that can be hammered or bent without losing its form or strength. Similarly, a pliable plastic is one that can be molded into various shapes without snapping or tearing. In contrast, a case-hardened metal or plastic is one that has been infused with carbon to make its surface extremely hard and wear-resistant, but also inflexible and brittle.