Toronto

Your comparing the population of the city of Toronto (631km^2) to the city of chengdu (14,378km^2) if your talking about unfair comparisons. The metro areas are closer in population chengdu (16m) vs Toronto (7m), so about double, and chengdu more then doubled Torontos metro construction.

Also If your talking about metro construction it might be better to look at production in general rather then population. Lagos in Nigeria has a similar population size to chengdu and the same sort of rapid growth over the past couple decades but nowhere near the same metro

If you look at gdp though it makes more sense, Lagos ($102b) has about a third the gdp of chengdu ($330b), which is about the size of Toronto ($473b). Even if you adjust for PPP chengdu ($707b), so similar to the population its a bit less then twice.

Chengdu is using its production capacity to build metros while Toronto is not. If Toronto chose to devote the same percent of there resources that chengdu has towards its public transit it could build a similar map to the above.