Here is the full list of all 20 Megacity Builder achievements.
4 Aerospace Factories
Win an air war
4 Automotive factories
Max civic buildings rating in any city
Raise 7 infantry units, 7 tanks units and 7 jet units.
150 Scientists
4 Electronics Factories
16 centrifuges
Production of 300 of each food item.
Production of 300 of each Resource
4 Heavy Industry factories.
Win a Land battle.
4 Light Industry factories.
Production Profits 300k+
City Popuatlion 1 million
2 Million Nation Population.
Nuke an enemy city.
1 million in the bank.
Get a Super Skyscraper.
Research a Tech Tree.