Complex sentence: Karachi (,/ALA-LC:) is capital of province Sindh as well as the largest and most populous metropolitan city of Pakistan and the 2nd-largest city in the world by population.
Split into simpler sentences: Karachi (,/ALA-LC:) is the capital of the province of Sindh, as well as the largest and most populous metropolitan city of Pakistan. It is the 2nd-largest city in the world by population.