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

Aguascalientes, Aguascalientes
Benito Juarez, Quintana Roo
Culiacán, Sinaloa
Durango, Durango
Ecatepec, State of Mexico
Fresnillo, Zacatecas
Guadalajara, Jalisco
Hermosillo, Sonora
Irapuato, Guanajuato
Juárez, Chihuahua
(no K)
León, Guanajuato
Mexico City, Mexico City
Nezahualcóyotl, Mexico City
Oaxaca, Oaxaca
Puebla, Puebla
Querétaro, Querétaro
Reynosa, Tamaulipas
San Luis Potosí, San Luis Potosí
Tijuana, Baja California
Uruapan, Michoacán
Veracruz, Veracruz
(no W)
Xalapa, Veracruz
Yuriria, Guanajuato
Zacatecas, Zacatecas