What is the prefix to blunt?

There isn't a single, commonly used prefix for "blunt." However, depending on the context, you could use:

* Un-: This suggests the opposite of being blunt, meaning something that is not blunt. For example, "unblunted criticism" would mean criticism that isn't direct or harsh.

* Pre-: This suggests something that comes before being blunt, implying a stage of preparation or development towards bluntness. For example, "pre-blunt negotiations" might imply that the negotiations haven't yet become direct and confrontational.

Ultimately, the best prefix to use depends on the specific meaning you're trying to convey.