The alphamegalog of the cities of Washington lists the largest city in Washington for each letter of the alphabet. In this case, ‘largest’ is based on population within the city proper.

Auburn
Belleview
Cottage Lake
Des Moines
Everett
Federal Way
Graham
Hazel Dell
Issaquah
Jamestown
Kent
Lakewood
Marysville
Newcastle
Olympia
Pasco
Quincy
Renton
Seattle
Tacoma
University Place
Vancouver
Walla Walla
(no X)
Yakima
Zillah