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

Aminabad, India
Beijing, China
Cairo, Egypt
Delhi, India
Ekurhuleni, South Africa
Foshan, China
Guangzhou, China
Ho Chi Minh City, vietnam
Istanbul, Turkey
Jakarta, Indonesia
Karachi, Pakistan
Lagos, Nigeria
Mumbai, India
New York City, USA
Osaka, Japan
Pune, India
Quanzhou, China
Rio de Janeiro, Brazil
Shanghai, China
Tienjin, China
Urumqi, China
Vienna, Austria
Wuhan, China
Xian, China
Yangon, Myanmar
Zhengzhou, China