What is a prefix for agreeable?

There isn't a specific prefix that directly means "agreeable." However, you could use prefixes to create words with related meanings, such as:

* Con-: *Convivial* (friendly and agreeable)

* Bene-: *Benevolent* (kindly and agreeable)

* Ami-: *Amiable* (friendly and agreeable)

* Pleas-: *Pleasing* (agreeable, enjoyable)

* Accep-: *Acceptable* (agreeable, satisfactory)

The best prefix to use would depend on the specific context and the nuance you want to convey.