Here's Northwest. Weak in Europe, non-existant in Africa, South America, and Australia, very strong in Asia, pretty good in the Caribbean and Mexico, and very good in Canada. Keep in mind that NW has very good reciprocal arrangements with KLM, so some of the gaps may not be as important as with other carriers.

NW
Europe
Paris
Amsterdam
London
Rome
Frankfurt
Asia
Singapore
Bangkok
Hong Kong
Manila
Taipei
Shanghai
Beijing
Seoul
Busan
Osaka
Nagoya
Tokyo
Saipan
Rota
Guam
Dehli
Mumbai
Caribbean
Liberia (CR) (S)
Nassau (S)
Grand Cayman (S)
Montego Bay
Puerto Plata (S)
Punta Cana (S)
San Juan (PR)
Mexico
Mexico City
Cancun
Puerto Vallarta (S)
Ixtapa (S)
Acapulco (S)
Cozumel (S)
Canada
Vancouver
Calgary
Toronto
Montreal
Ottawa
Quebec (S)
Edmonton
Saskatoon
Winnipeg
Regina
Thunder Bay
London