1997 MIT Mystery Hunt Puzzle 27 Solution

You should notice that many of the answers have uncommon letters. Each of the starred columns is meant to contain 25 different letters of the alphabet, and the missing ones spell the answer.

TWELVEGOP
URDUNAVEL
ROWLFSKIS
INVIOLATE
AGARBARQS
EXTOLAQUA
OKJOURNAL
ABBAQUICK
ITCHKICKS
OFFEXEMPT
DMZSPAWNS
ALONZOJVC
RHYTHMTWA
EZRASOPHS
OVIDJESSE
MEXICOYYZ
BJSURHOFF
ASHAMEDJO
NIKAGOLGI
GYPSYAFRO
EQUITABLE
SPLEENXXX
PAQUINHMS
EDGEARUBA
ACMEDIZZY
 UN W ED

The answer is UNWED