What prefix can be used for courteous?

There isn't a single perfect prefix to make "courteous" into a new word. However, depending on the desired nuance, you could use:

For emphasis:

* Ultra-courteous: This emphasizes a very high degree of courtesy.

* Super-courteous: Similar to "ultra-courteous," this emphasizes a high level of courtesy.

For formality:

* Formal-courteous: This emphasizes the polite and formal nature of the courtesy.

For specific contexts:

* Diplomatic-courteous: This implies courtesy used in a diplomatic or political setting.

* Professional-courteous: This implies courtesy used in a professional context.

Other possibilities:

* Exceedingly courteous: This emphasizes a high level of courtesy.

* Eminently courteous: This emphasizes a very high level of courtesy.

Ultimately, the best prefix will depend on the specific context and the desired meaning.