pangrammatist
/ˌpanˈɡramətɪst/ /ˌpaŋˈɡramətɪst/noun
A writer who uses every letter of the alphabet in a single sentence, line of verse, etc.; a composer of pangrams.
Origin
Mid 18th century. From pan- + ancient Greek γραμματ-, γράμμα letter + -ist, after anagrammatist.